DEPARTMENT OF THE INTERIOR ALBERT B. FALL, Secretary UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director

Bulletin 679

THE MICROSCOPIC DETERMINATION OF THE NONOPAQUE MINERALS

BY

ESPER S. LARSEN

WASHINGTON GOVERNMENT PRINTING OFFICE 1921

CONTENTS.

CHAPTER I. Introduction...... 5 The immersion method of identifying minerals...... 5 New data...... 5 Need of further data...... 6 Advantages of the immersion method...... 6 Other suggested uses for the method...... 7 Work and acknowledgments...... 7 CHAPTER II. Methods of determining the optical constants of minerals ...... 9 The chief optical constants and their interrelations...... 9 Measurement of indices of refraction...... 12 The embedding method...... 12 The method of oblique illumination...... 13 The method of central illumination...... 14 Immersion media...... 14 General features...... 14 Piperine and iodides...... 16 Sulphur-selenium melts...... 38 Selenium and arsenic selenide melts...... 20 Methods of standardizing media for measuring indices of refraction. 20 Measurement of all indices of refraction of crystals...... ^...... 22 Measurements of axial angles...... 24 Dispersion of the optic axes...... 25 Optical character...... 25 Optical orientation, dispersion of bisectrices, and crystal system...... 26 Other tests...... 27 CHAPTER III. Some statistics on the optical properties of minerals...... 28 Distribution of minerals with regard to optical character...... 28 Distribution of minerals with regard to index of refraction and birefringence. 28 Relation between index of refraction, density, and chemical composition . 30 CHAPTER IV. Measurements of optical properties of minerals...... 33 Completeness and accuracy of the data...... 33 The new data...... 34 CHAPTER V. Tables for the determination of minerals from their optical prop­ erties...... 161 Arrangement of the data in the tables...... 161 Completeness of the data...... 162 Tables...... 16 3 List of minerals arranged according to their intermed iate indices of refraction, /?, and showing their birefringences...... \...... 163 Data for the determination of the nonopaque minerals...... 171 Isotropic group...... 171 Uniaxial positive group...... 185 Uniaxial negative group...... 192 Biaxial positive group...... 205 Biaxial negative group...... 241 Minerals of unknown optical character...... 279 INDEX ...... 285 3 ILLUSTRATIONS.

PLATE I. Case carrying dropping bottles with index of refraction media...... 16 FIGURE 1. The error in V'« as computed from the approximate formula

Cos2 V'«=^-...... « j a 11 2. Indices of refraction of mixtures of piperine and iodides...... 17 3. Indices of refraction of mixtures of sulphur and selenium...... 19 4. Diagram showing density of distribution of the nonopaque minerals with respect to the intermediate index of refraction...... 29 5. Diagram showing density of distribution of the nonopaque minerals with respect to index of refraction and birefringence...... 29 6. (Optical orientation and zonal growths of annabergite on tabular face {010}...... 40 7. Optical orientation of tabular crystals of churchite...... 58 8. Optical orientation of common cleavage fragments {010} of haiding- erite...... 82 9. Optical orientation of tabular crystals {100} of larderellite...... 98 10. Optical orientation of tablets {100} of martinite...... 105 11. Optical orientation of tablets {010} of artificial sodium bicarbonate. 134 12. Optical orientation of tabular crystals of voglite...... 154 13. Optical orientation of tabular {010} crystals of walpurgite...... 156 14. Optical orientation of tabular crystals of zinkosite...... 159 4 THE MICROSCOPIC DETERMINATION OF THE NONOPAQUE MINERALS.

By ESPER S. LARSEN.

CHAPTER I. INTRODUCTION. THE IMMERSION METHOD OF IDENTIFYING MINERALS. Optical methods of determining minerals with the petrographic microscope have long been used and have been carried to a high state of development in studies of the minerals in thin sections of rocks and ores, yet out of about 1,000 mineral species comparatively few can be identified readily in thin sections. A mineral whose optical properties are known can be accurately and quickly identi­ fied, however, by the immersion method that is, by immersing its powder in liquid media whose indices of refraction are known and determining its optical constants. In this bulletin the author gives a set of tables for the systematic determination of minerals from their optical constants, describes briefly some methods for the rapid determination of optical constants, gives the results of measurements of the optical constants of more than 500 species for which data was not previously available, and presents statistics on the optical properties of minerals. The first tables prepared for general use in determinations of minerals by the immersion method were those of Van der Kolk,1 published in 1900. Somewhat similar tables, prepared by A. F. Rogers,2 were published in 1906, and an optical mineralogy con­ taining tables and description of all minerals for which optical data were then available, prepared by N. H. and A. N. Winchell,3 was published in 1909. However, the method has not received the attention that it deserves and has not come into general use, largely because the optical constants of over half the known minerals had not been determined. NEW DATA. In attempting to employ the immersion method some years ago the writer assembled all the data then available for its use with the petrographic microscope in determining minerals but found them so

1 Schroeder van der Kolk, J. C., Tabellen zur mikroskopischen Bestimmung der Mineralien nach ihrem Brechungsindcx, Wiesbaden, 1900; 2d ed., revised and enlarged by E. H. M. Beekman, 1906. 2 Rogers, A. F., School of Mines Quart., vol. 27, pp. 340-359,1906. ' Winchell, N. H. and A. N., Elements of optical mineralogy, D. Van Nostrand Co., 1909. 5 6 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

incomplete that the method was applicable to but few species. Since then he has measured the chief optical constants of over 500 mineral species for which the data were lacking or incomplete, so that such data are now lacking for only about 30 very rare species. No attempt at great accuracy was made in these measurements, and compara­ tively few of the specimens studied represented analyzed minerals. Only a small number of minerals of many isomorphous series were examined, in some series only a single member. NEED OF FURTHER DATA. Much further work on the optical constants and more complete and accurate data on nearly all the minerals are needed, as well as detailed studies of isomorphous series and of the effect of solid solution. Another need is a fuller appreciation of the fact that most minerals are of variable chemical composition and therefore have variable optical and other properties. The science of mineralogy needs also good connected and consistent data on minerals. Chemical analyses, crystallographic studies, and determination of physical properties, optical constants, and paragenesis should be made on identical material. A highly accurate determination of the optical or other constants of a mineral is of comparatively little value unless the data obtained are definitely tied to a chemical analysis. Greater care should be taken in examining minerals for lack of homogeneity, whether it is due to zonal growths or to admixed or included foreign material. As few specimens of minerals are entirely free from foreign bodies and without zonal growths or other elements of heterogeneity no description of a mineral is adequate which does not show clearly that its material has been carefully examined microscopically. Every published analysis of a mineral should include a clear statement of the approximate amount and the character of the foreign material it contains and of the degree or extent of zonal growths or other elements of heterogeneity; and this statement should be the result of a careful microscopic examination of a sample of the same powder that furnished the material for the chemical analysis.

ADVANTAGES OF THE IMMERSION METHOD. For determining the nonopaque minerals the immersion method has many advantages over other methods. It appears to excel greatly the ordinary blowpipe methods in rapidity and accuracy, and the quantity of material required is less than that required for tests by any other method. One who has acquired the requisite skill can measure the principal optical constants of a mineral in about half an hour, and most minerals can be determined by partial measurements in less tune. In accuracy the method is nearly as reliable as a com­ plete chemical analysis, for it is about as common for two or more INTRODUCTION. 7 minerals to have the same chemical composition as for two or more minerals to have the same optical constants. All the optical prop­ erties of a mineral can usually be determined from a single grain or crystal large enough to handle with a pair of delicate pincers, and in addition the material can be examined for homogeneity when the tests are made. Lack of homogeneity in material studied is one of the chief sources of error in mineralogic work. The skill required to measure the optical constants is little if any greater than that required to do reliable blowpiping. The worker must have a good knowledge of optical mineralogy, such as may be gained by any good course in microscopic petrography, and some special training in the manipulation of immersed grains of minerals. The only equipment required is a good petrographic microscope and a few inexpensive liquids whose indices of refraction are known. OTHER SUGGESTED USES FOR THE METHOD. The optical method might be used with advantage in work done in a number of other branches of science than mineralogy and in some industries. It should be much more generally used in chemistry, es­ pecially in analyses of artificial crystalline products, to determine rapidly the exact nature of the material and its homogeneity, for artificial products have as definite optical constants as minerals. It should also be found valuable in many metallurgic processes, as well as in the cement and ceramic industries and other industries in which a knowledge of the exact nature of any material is desirable.

WORK AND ACKNOWLEDGMENTS. The writer began his work on the tables in 1909, intending to measure the constants of only a few of the commoner minerals, but the desira­ bility of having optical data on all the recognized species of minerals became so apparent that he afterward undertook the task of making all the measurements desired. Most of the work was done in the lab­ oratory of the United States Geological Survey at Washington, D. C., but a considerable part was done at the University of California at Berkeley, Calif., during the winter of 1914-15. To measure the optical constants of 500 selected minerals is no great task, but difficulties appeared continually as the work progressed, owing to the frequent necessity of selecting suitable material from specimens consisting largely of other minerals, to the large number of specimens that were found to be incorrectly labeled, and to the difficulty of procuring many rare minerals. The writer wishes to express his sincere thanks to Messrs. H. E. Merwin and Fred E. Wright, of the Geophysical Laboratory, W. T. Schaller, of the Geological Survey, and E. T. Wherry, of the National Museum, for help and encouragement in the work. Thanks 8 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. are due also to Messrs. Merwin and Schaller for critically reading the manuscript of this bulletin and offering many helpful criticisms and suggestions and for furnishing unpublished data on a number of minerals. The writer wishes also to express his appreciation of the generosity of the officials of a number of museums and of several private collectors of minerals in furnishing specimens of many rare and valuable minerals. He is especially indebted to Col. Washington A. Roebling, of Trenton, N. J., who very generously placed his remarkable collection at the writer's disposal; to the late L. P. Gratacap and the American Museum of Natural History; and to Dr. Edgar T. Wherry and the United States National Museum. He is also grateful, for many valuable specimens of the rarer minerals, to Prof. W. E. Ford and Yale University; Prof. Charles Palache and Harvard University; Prof. A. S. Eakle and the University of California; Prof. A. H. Phil­ lips and Princeton University; Johns Hopkins University; Prof. Oliver C. Farrington and the Field Museum of Natural History; Mr. F. McN. Hamilton and the California State Mining Bureau; Mr. F. A. Canfield, of Dover, N. J.; Dr. Per Geijer, of Stockholm, Sweden; and Prof. A. Lacroix, of Paris. CHAPTER II. METHODS OF DETERMINING THE OPTICAL CON­ STANTS OF MINERALS. In this chapter the writer describes briefly the special methods which he has found most satisfactory for the rapid determination of the principal optical constants of minerals by the immersion method. The chapter is not intended to be a complete discussion of optical mineralogy, and in order to understand it properly, the reader should have an elementary knowledge of crystallography and of the methods of optical mineralogy.4 Theoretical discussions are avoided as far as possible, and no attempt is made to describe the methods of measuring accurately the optical constants of minerals.5

THE CHIEF OPTICAL CONSTANTS AND THEIR INTER­ RELATIONS. The significant fundamental optical constants of crystals are the principal indices of refraction, the crystallographic orientation of the directions of vibration corresponding to these indices of refraction, and the amount of absorption of light vibrating in these directions, all for one or more standard wave lengths of light. For most minerals some of the constants, particularly the last, are known only in a qualitative way. The other properties commonly mentioned among the optical constants birefringence, optical character, optic axial angle, dispersion of the optic axes, dispersion of the bisectrices, extinc­ tion angle, color, and pleochroism are fixed by the fundamental constants and are significant only because they are often easily measured or estimated under the microscope. Different symbols are used by different writers in referring to certain optical properties. Those used here are perhaps as commonly used as any in the textbooks listed below.4 Refractive indices a,

4 Iddings, J. P., Eock minerals, John Wiley & Sons, 1911. Weinschenk-Clark, Petrographlc methods, McGraw-Hill Book Co., 1912. Johannsen, A., Determination of rock-forming minerals, John Wiley & Sons, 1908. Winchell, N. H. and A. N., Elements of optical mineralogy, D. Van Nostrand Co., 1909. Groth- Jackson, Optical properties of crystals, John Wiley & Sons, 1910. Edwards, M. G., Introduction to optical mineralogy and petrography, Cleveland, Ohio, 1916. Finlay, G. I., Igneous rocks, McGraw-HillBook Co., 1913. Luquer, L. M., Minerals in rock sections, D. Van Nostrand Co., 1905. Dana, E. S., A textbook of mineralogy, John Wiley & Sons, 1916. Moses, A. J., and Parsons, C. L., Elements of mineralogy, crystal­ lography, and blowpipe analyses, D. Van Nostrand Co., 1916. 6 A comprehensive treatment of the accuracy and limitations of the methods of optical mineralogy, based upon theory and checked by observations, isgiven by Fred. Eugene Wright in The methods of petrographlc- microscopic research: Carnegie Inst. Washington Pub. 158, 1911. Albert Johannsen:s Manual of petro- graphic methods, published by the McGraw-Hill Book Co., 1914, is an excellent compilation of the methods that have been proposed for optical measurements with the microscope. Rosenbusch's Mikroskopische Physiographic der Mineralien und Gesteine, Band 1, Erste TJalfte, by E. A. Wulfing, 1904, and Groth's Physikalische Krystallographie, 4th ed., 1905, are valuable books of reference, as is also Duparc and Pearce's Trait6 de technique mineralogique et pe'trographique, pt. 1,1909. 9 10 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. j8, 7 have directions of vibration X, Y, Z; birefringence is represented by B and equals y a or w e or e co. The relations that exist between the various optical properties are of considerable significance, and the author believes that they are not sufficiently emphasized in the textbooks nor are they kept clearly enough in mind by workers in optical mineralogy. The best available data on over 30 mineral species, or nearly 10 per cent of those for which data were available, can be seen at a glance to be strikingly inconsistent, and this happens even where the data appear to have a high degree of accuracy. The following examples will serve to illustrate: Leucosphenite is said to be optically negative, but the values given for the indices of refraction (a?/ = 1.6445, /3W = 1.6609, yv = 1.6878) are those of an optically positive mineral. Tests by the author show that leucosphenite is optically positive. Lawsonite is stated to have the following properties: a = 1.6650, 0 = 1.6690, 7 = 1-6840, 2V = 84° 6', optically +. The axial angle, as computed from the indices of refraction, is 2V = 54°. It seems probable that the axial angle is correct and that /3 should be about 1.6735. The relation between the axial angle (2V) and the indices of refraction is expressed by the equation :6

7 a holds fairly well if the axial angle is small or the birefringence not too strong. The error in V'a, as computed from the approximate formula, is shown in figure 1. The calculated value of V'a is along the abscissa, and the correction to be added to this value is along the ordinate. For all the curves the value of a is 1.500, and each curve is for a particular value of 7 a = B. The curves can be used to correct calculations made by the approximate formula. In the accurate equation a, /3, or 7 appear in the same power in both the numerator and denominator, so that the value of the equation will not be changed if they are replaced by pGL -p/J and -r-'Y Hence to apply

s For the development of this equation see Johannsen's Manual of petrographic methods, p. 103, 1914; Rosenbusch (Wulfing) Mikroskopische Physiographic, Band 1, Erste nalfte, p. 96, 1904; Groth-Jackson, Optical properties of crystals, p. 143, 1910; Duparc and Pearce, Traite" de technique mine'ralogique et pe"trographique, pp. 78-80, 1907. For tables and a graphic solution of this equation see Wright, F. E., Graphical methods in microscopical petrography: Am. Jour. Sci., 4th ser., vol. 36, pp. 517-533,1913. 7 For a graphic solution of this equation see Wright, F. E., The methods of petrographic-microscopic re­ search: Carnegie Inst. Washington Pub. 158, pi. 9,1911. METHODS OF DETERMINING THE OPTICAL CONSTANTS. 11 the correction from the curves to a crystal with a different from 1.500 1.500 it is necessary to calculate B' = (7 a). The value of B' need be calculated only approximately. To get the correct value of V« from the indices of refraction the approximate value V'a should be found from the equation Cos2 V'a = 7*-Q!- or from the 1 50 graph; then B'= ' (7 a) and from these two values the correc­ tion to be added to V'« may be read from figure 1. The formulae given above indicate the value for the angle about a, which may be either the acute bisectrix (Bxa) or the obtuse bisec­ trix (Bx0). By definition, if a is the acute bisectrix (Bxa) the

FIGURE 1. The error in V'a as computed from the approximate formula Cos2 va~-^-- mineral is optically negative and 2Va is less than 90° (Va <45°). As tan 45° = 1, a mineral is optically negative if 2 ^ > -^ 2 and opticallyr j positiver if a,i -5*pz <-3-,pt ^2, Cos 45° = -1= for an optically negative mineral from the approximate formula r^ i or 2 0? a) > (7 a) approximately. Similarly for an optically positive mineral 2 (7 ft) > (7 a) approxi­ mately. These approximations hold only where the birefringence is not too strong. The following values of a, /3, and 7 are for crystals where 2V = 90° and show the increasing error in the approximations as the birefringence increases : a=1.5000 /3=1.5099 7=1.5200 a=1.5000 0=1.5244 7=1.5500 a=1.5000 0=1.5476 7=1.6000 a=1.5000 0=1.5906 7=1.7000 a=1.5000 0=1.6297 7=1.8000 12 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

The axial angle is commonly measured in air, and the apparent axial angle so measured (2E) has the relation to the true axial angle 2V expressed by sin E = /3 sin V, where /3 is the intermediate index of refraction of the mineral.8 In the preceding equations the values are given for light of a particular wave length. As the wave length varies the indices of refraction and consequently 2V will vary, and even the optical character may change. This variation is called the dispersion of the optic axes, and 2V may be given for different colors or it may be given for one color commonly the yellow light of sodium and the variation with color may be expressed .by pv), meaning simply that the axial angle is less (or greater) for red than for violet. Not only do the values of the indices of refraction change with the color of light, but the positions of two of the directions X, Y, and Z in monoclinic and of all three in triclinic crystals change that is, the extinction angles vary with the color of light. This variation is. called dispersion of the bisectrices. Crossed, horizontal, and inclined dispersion are simply phenomena due to dispersion of the bisectrices as observed on the interference figure.

MEASUREMENT OF INDICES OF REFRACTION. The indices of refraction of a mineral can be measured most con­ veniently and accurately on a polished surface with the total refracto- meter or somewhat less conveniently on specially prepared and oriented prisms by the method of minimum deviation. Most min­ erals are not suitable for measurement by either of these methods, either because suitable plates or prisms can not be prepared or because the mineral is zoned and so differs in its optical properties at least as much as the error in the less accurate but much more: rapid embedding method.

THE EMBEDDING METHOD. Fairly accurate measurements of the principal indices of refrac­ tion can be made on a very small quantity of mineral by embedding the powdered grains in media whose indices of refraction are known and comparing and matching the indices of the media with each of those of the mineral by either the method of central illumination or the method of oblique illumination. The method of oblique illumination is best used with an objective of low or moderate power and can therefore be applied to a large number of grains very quickly. The method of central illumination is best used with an objective of moderate or high power.

8 For a graphic solution of this equation see Wright, F. E., op. cit., pis. 7 and 8, 1911. METHODS OF DETERMINING THE OPTICAL CONSTANTS. 13

THE METHOD OF OBLIQUE ILLUMINATION.9 The index ttf refraction of a grain embedded in a liquid or other body and that of the embedding material can be quickly com­ pared by observing their line of contact under the microscope and shading a part of the field by placing the finger or a card beneath the condenser system, by tilting the mirror, or in some other way. A number of devices have been recommended for this purpose, and some of the newer microscopes have special slides inserted. The observation is best made with a low or moderate power objective and without the condenser lens. With a low-power objective a mineral that has a decidedly higher index than the liquid will have a dark border toward the shaded side of the field and a bright border on the opposite side. If the grain has a decidedly lower index of refraction the phenomena are reversed and the bright border is on the shaded side of the field. With the moderate-power objective and the condenser lens the phenomenon depends on the position of the condenser. If the focus of the condenser is above the object the phenomena are as stated above; if below the slide, the phenomena are reversed. It is best to check the system used by making the test on some known grain; a thin section in which orthoclase, quartz, or some other known mineral is in contact with Canada balsam is good for this purpose. At the same time the difference in index of refraction between the grain and liquid can be estimated by the relief and the amount of shading required to bring out the relief. This method is equally well adapted to thin sections and has many advantages over the Becke method or the method of central illumi­ nation, as it can be used with a low-power objective, and by it every grain in contact with the Canada balsam can be compared with balsam in a very short time. For simplicity, the grain may be considered isotropic. If mono­ chromatic, light is used, and if the grain and liquid have the same index of refraction for that light and are clear and colorless the grain will completely disappear. As most of the liquids commonly used have a stronger dispersion than most minerals, if the mineral and liquid have the same index for sodium light the mineral will have a higher index for the red end of the spectrum and a lower one for*the blue. Hence, if white light is used there is a concentra­ tion of reddish light on one side of the grain and of bluish light on the other side. For some of the immersion materials notably cinnamon oil the dispersion is very great and strongly colored borders are present even where the index for sodium light of the grain and the liquid differ in the second decimal place. The relative indices must be judged from the intensities of the colors. In order

« Wright, F. E., The methods of pctrographic-microscopi c research: Carnegie Inst. Washington Pub. 158, pp. 92-95,1911. 14 MICEOSCOPIC DETERMINATION OF NONOPAQUE MINERALS. for the worker to become familiar with the color phenomena under various conditions it is well to immerse grains with known indices of refraction in oils of known indices of refraction. For this purpose co of quartz or of calcite is constant.

THE METHOD OF CENTRAL ILLUMINATION. As the immersion method is ordinarily used nearly all fragments are thinner on the edges than in the center, and if the fragments differ from the surrounding material in refractive index they will act as small imperfect lenses toward a beam of nearly parallel light emerging from the condenser. If such a lenticular fragment has a higher index of refraction than the embedding medium it tends to focus the light above its plane, and if the microscope is first focused on the grain and then raised above focus the interior of the grain will appear more highly illuminated. As the microscope tube is raised higher above focus this highly illuminated area contracts and becomes brighter a bright line moves into the grain. If the tube is lowered below focus the grain appears less highly illuminated than the rest of the field and a highly illuminated halo surrounds it. As the tube is lowered this halo moves out from the grain. If the grain has a lower index of refraction than the embedding medium it will have a virtual focus below its plane, the phenomena are reversed, an^. the grain becomes centrally illuminated as the mi­ croscope tube is lowered below focus. In practice the test is best made with an objective of medium or high power one with 8-millimeter focus gives good results. The con­ denser may be in or out. The condenser system may be lowered or the lower diaphragm closed. The most suitable arrangement for a particular microscope and lens system can best be found by testing it with grains embedded in media of known indices of refraction.

IMMERSION MEDIA.

GENERAL FEATURES. Immersion media should be nearly colorless, chemically stable, and without disagreeable odor or other objectionable properties. They should not dissolve or react with the mineral to be immersed. Low volatility and for many purposes a moderate though not too great viscosity are desirable. Each liquid should be miscible with the liquids whose indices of refraction are above and below it, and two liquids that are to be mixed should have approximately the same rate of volatilization, as otherwise the mixture may change rapidly. The index of refraction should not vary too greatly with changes of tem­ perature. A low dispersion is desirable for accurate work, but a rather strong dispersion facilitates rapid determination. The author has found the set of media given in Table 1 satisfactory, and it covers the range of nearly all the minerals. METHODS OF DETERMINING THE OPTICAL, CONSTANTS. 15 Satisfactory liquids cover the range of indices of refraction up to 1.87 and above that point low-melting mixtures that remain amorphous on cooling may be prepared which cover the range up to 7iLl = 3.17. The values for the indices of refraction (n) are for sodium light except where noted for the sulphur-selenium and selenium-arsenic selenide melts and are those determined by the author at about 20° C. for liquids purchased in the ordinary market. In the column marked -57-(LTL is given the change in the index of refraction for each degree centigrade change in the temperature. For all the media given the index of refraction decreases as the temperature increases. These values are mostly taken from the literature. The liquids are rather inexpensive, excepting methylene iodide. All the liquids, except as noted, will form suitable mixtures with those above and below in the table in all proportions. Amyl alcohol is unfortunately a solvent for a number of the minerals that have indices of refraction within its range, and measurements with it must be made rapidly.

TABLE 1. Refractive indices of immersion media.

n at 20° C. dn Dispersion . Remarks. di

TtTpf-nr 1.333 Slight... Dissolves many of the minerals with low indices. Acetone...... 1. 357 " "6." 66646' Slight...... 1.302 .....do...... Do. 1.381 .....do...... Methyl butyrato ...... 1.386 .....do...... 1. 393 .....do...... 1.409 0. 00042 .....do...... Dissolves many minerals with which it i s used. 1.448 0. 00035 .....do...... Petroleum oil:& Russian alboline ..... 1.470 0.0004 .....do...... American alboline. . . . 1.477 0. 0004 .....do...... 1.502 0. 0004 .....do...... Will not mix with clove oil. 1.531 0. 00050 Moderate.... Will mix with petroleum oil. 1.585 to 1.600 0. 0003 Strong ...... Cinnamon oil from Ceylon 1.595 0. 0003 .....do...... 1.614 to 1.617 0. 0003 .....do...... a Monobromnaphtha- 1.658 0. 00048 Moderate.... lene/. 1.737 to 1.741 0. 00070 Rather Rather expensive. Discolors on expo­ strong. sure to light, but a little copper or tin in the bottle will prevent this change. Methylene iodide satu­ 1.778 .....do...... rated with sulphur. Methylene iodide, sul­ 1.868 .....do...... phur, and iodides, g Pipeline and iodides ..... 1.68 to 2.10 Sulphur and selenium. . . . 1.998Na to Very strong. 2.7l6Li Selenium and arsenic 2.72to3.17Li .....do...... selenide.

a Ordinary fusel oil may bo used, but on mixing with kerosene it forms a milky emulsion, which settles on standing, and then the clear liquid may bo decanted off. i> Any of the medicinal oils may be used, such as Nujol. c Any good, cleanlubricating oil, such asi s used in automobiles, may be used. d If clove oil does not mix with petroleum oil mix it with rapeseed oil. n= 1.471. e The only advantage in using cinnamon oil is that it is less expensive than cinnamic aldehyde. / Mixtures of clove oil and a monobromnaphthalene give a set'of liquids of lower dispersion than those with cinnamon oil. g To 100 grams methylene iodide add 35 grams iodoform, 10 grams sulphur, 31 grams Snl4,16 grams Asia, and 8 grams 80X3, warm to hasten solution, allow to stand, and filter off undissolved solids. See Merwin, H. E., Media of high refraction: Washington Acad. Sci. Jour., vol. 3, pp. 35-40,1913. 16 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. For fairly accurate work it is desirable to have a set of liquids from n.= 1.400 to n= 1.87, differing from each other by 0.010, and a set of the solid media to carry the series up to n = 2.72, the index of these media differing by 0.020. For less accurate work the set can be re­ duced to suit the requirements. The most important range is from 1.45 to 1.87, as j8 for about 80 per cent of all the known nonopaque minerals falls within this range. There are only about eight minerals in which /3 is below 1.40 and only about 24 in which j3 is above 2.72. Care should be taken to prevent contamination and evaporation of the liquids. They are best kept in tall dropping bottles that have the combined ground stopper and dropper with glass cap. (J^ 15 cubic centimeter bottle is the smallest that is kept in stock by dealers, and even that size is larger than is required for the ordinary amount of work. It is best to keep the bottles at least half full, but with methy- lene iodide economy may dictate the use of a smaller amount. The bottles should never be allowed to stand without the stopper and cap in place. A convenient and easily made case for the bottles is com­ posed of a covered box that opens on hinges at one end. Ten bottles are kept in a 2-inch board which has 10 holes just large enough to hold the bottles. (See PL I.) The box is made to take as many of these boards with the bottles as desired. The box should be kept closed, as light affects some of the liquids, notably methylene iodide. Small glass tubes with glass rods inserted in the cork stoppers are satisfactory for liquids between 1.40 and 1.67. With proper care a set of liquids made up as directed above will remain constant, within the limits of error required for most deter­ minative work, for years. A set of 40 such liquids, used constantly for five years and checked once or twice a year, has rarely shown a change in any of the liquids of as much as 0.003. One or two liquids that have methylene iodide as a constituent were nearly all used up and had changed as much as 0.006. In general the liquids whose indices of refraction are above 1.75 are less constant. The embedding media whose indices of refraction are above 1.87 are solid at ordinary temperature and are not quite so convenient nor accurate as are the liquids. They must not be heated too hot nor too long or they will change considerably. A small electric plate with three grades of heat is a convenient means for making embeddings with these melts. In practice a very small amount of the embedding medium is melted on a glass slip, a little of the powder to be examined is dusted into the melt, and a cover glass is pressed down upon it. In the highly colored melts that are rich in iodides or selenium the mineral must be powdered very fine, otherwise the thick film of the melt is nearly opaque. PIPEBINE AND IODIDES.10 Molten piperine dissolves the tri-iodides of arsenic and antimony and forms solutions that are fluid at slightly over 100° C. and are i" Merwin, H. E., Media of high refraction for refractive index determinations with the microscope: Washington Acad. Sci. Jour., vol. 3, pp. 35-40,1913. TJ. 8. GEOLOGICAL SURVEY BULLETIN 679 PLATE I

CASE CARRYING DROPPING BOTTLES WITH INDEX OF REFRACTION MEDIA. METHODS OF DETERMINING THE OPTICAL CONSTANTS. 17 resin-like and amorphous when cold. To make such preparations having constant indices of refraction anywhere within the range 71 = 1.68 to 2.10, mix three parts by weight of SbI3 to one part of AsI3, add this mixture to the piperine in the proper proportion, and heat carefully and stir in a test tube, large porcelain crucible, or glass flask just above the melting point of piperine until a homo­ geneous melt is obtained. A few grams of such a melt are sufficient for a large number of immersions. The heating may be done in 210

orLJ U. 135 o X U

10 20 30 40 50 60 70 90 °/o IODIDES' FIGURE 2. Indices of refraction of mixtures of piperine and iodides. a bath of crisco or paraffin, in an air bath, or over but not in the low flame of a bunsen burner or on an electric plate; stirring is essential to secure homogeneity. If the preparations are heated too hot the piperine is decomposed. The iodides should be examined under the microscope for impurities. Such preparations can be standard­ ized on the goniometer by measuring a prism molded between two pieces of cover glass, or weighted quantities of the constituents can be used and the refractive indices of the resulting preparation obtained from figure 2. The indices of refraction of such media increase rather rapidly on standing, and they are not entirely con- 12097° 21 2 18 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. stant for about a month.11 The total increase in this time amounts to a few units in the third decimal place. After that time the indices remain constant and reheating does not affect them. In figure 2 curve a shows the indices of freshly made preparations and curve 6 the indices of the preparations after they have stood until constant. The indices of refraction as measured in white light in these melts (above n = 1.70) are almost those for sodium light.

SULPHUR-SELENIUM MELTS. Melted sulphur and selenium in any proportion readily form a homogeneous solution which has a constant index of refraction on cooling and remains amorphous long enough to allow measurements to be made. Suitable preparations with any index of refraction from 2.05 to 2.72 can be made by mixing the constituents in the proper proportion by weight and heating in a test tube just above the melting point until homogeneous. The mixture must be stirred and any sulphur that condenses on the upper part of the tube scraped back into the melt. The refractive indices for melts with different proportions of sulphur and selenium for light of different wave lengths are given in figure 3, and preparations having approxi­ mately any index of refraction can be made by using weighed quantities of the constituents. The indices of refraction of melts that contain more than 50 per cent of sulphur differ considerably according to the treatment, and this difference, which is probably due 'to the presence of X and fj. sulphur in different proportions, increases with the amount of sulphur.12 By high heating and quenching the index of refraction may even be raised 0.05 above that obtained by cooling in air. The proper treatment is to heat a small amount of the material on an object glass considerably above tne melting point until the dark form of sulphur is obtained, then to add the mineral grains, press down a cover glass, and cool rather rapidly on a damp but not wet cloth or on an iron plate. It must also be remembered that sulphur is rather volatile. If the mineral to be tested is not decomposed by heating, it is well to mix the powdered embedding material and the mineral and to cover with a cover glass before heating, or to add the grains and cover before the final high heating. With proper care an accuracy of about ±0.01 can be attained. Indices of refraction for sodium light below about 2.20 can be readily measured in the sulphur-selenium melts, but above that

» For this and much other information about the preparation of melts for high index determinations I am indebted to a personal communication from Dr. H. E. Merwin. 12 Merwin, H. E., and Larsen, E. S., Mixtures of amorphous sulphur and selenium as immersion media for the determination of high refractive indices with the microscope: Am. Jour. Sci., 4th ser., vol. 34, pp. 42-47,1912. METHODS OF DETERMINING THE OPTICAL CONSTANTS. 19 point, on account of the deep-red color of the melts and the very strong dispersion of selenium, it is best to make the measurements for the red light of lithium. This operation can be easily done by

%Se 6O 7O 8 0 9 0 2 05 100 ^ ^ ~1 " ~ 65O j 1 ~£_ i / 1 f _ It- Li 2.7 --- - I / 1 2 1 7_ ^ / 1 > i 1 1 t / *_ f / I / / ^ / / 1 / 1 7 / / 1 7 / / / f / f 17 f, 2.6 ---- 1 / / / 1 / J / y 1 t 7 ' / t f ( / 1 / / / 1 f i f 1 / ) / rf ^ 1 J / 1 1 / 1 , / / j / ,' ,' T f ^ f / t / , 2.5 ------,. / f i / / / / ! / f ' f ^ ,/ / / / f / / / ,/ / f f / / ' / ,/ , f ^ t °t , , / ^ / / / ' / / / , ' 7 y ,/ / / ' / / /J / / , , / , / / / / ' 2.4 / / / ^ / / / / y . ^ ^ / / / / / / / ,, ^ / / ,/ / f / / ^ / /ni' / , ^ /Lx ' £_ / ' 7 ' / ^_ , ' / x "7 7 / ^ X . "" .^ ' t' !/ 7 / / X1 / 'x 7 / ^ /-Z/, / ___.__,_ ** £ ~?*~~ / ' x x , ^ / X .. ^ ' s ^ ' ^ Tl X x ' ^ 7 X x X 7 T 1 \ 7 SSO 7 / S-e. X ^ f x. S50 7 , x X x 7 , , £ *" ' ' *-. x . 7 "? x ^ ' x. ^ X- S ' X . ' X x' , \s x s * Na ~ 2.2 £^x x ^ /" x 7* -^ x s ''* BOO" x ' x Xx x X s X x s*" x ^ x 7 X x 7 ' rk x* X eso ^ ' ~ ^ ^ ' X X ' X f f x x X '"x- LI x x t x x X x k X x' ^ * lx x X X , x X X x x X x ' * x^ X X x^1 ,* "" « ' x' " X ** x ^ x x x x x X X , ' I ., ^ ^' »* ' * ' '. X x X x *" X JUlAl 2.1 ------" X *" ~ . x ^ < ^ & Lir X - - x ___.,^::^ y^:-- - :?- ~ p= ^ -^ x 7 X x - *" - * p x-" x^ >^^.-*'"'?< ^» ' - k: ---?-*- _-,^-, i ;="-^ b;^" 5 ; ^ X -- ^- -" 31 ''' x ""-- . ^ ,-;^-- ^! ;. --- " ^ "" « " *" x^^- ''*' '' ' V*'^ '-^ "" ^ *" °" -" ^ ~ Z-^ ^ *~^--~ -, 0'Z-'Z-^' Z.-r'Z.- ~*.-~~-^ ,-r^ -~ ; -- " t "z.'^-Z.'^.-Z.'Z n ______oo Pn J 1 -, TO 20 30 40 50 FIGURE 3. Indices of refraction of mixtures of sulphur and selenium. placing over the eyepiece a color screen made by pressing a thin film of the melt composed of 70 per cent selenium and 30 per cent sulphur between two glass plates, as such a film transmits chiefly 20 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. light that is about equivalent to lithium light. Such a film crystal­ lizes very slowly. Mixtures containing over 70 per cent selenium transmit chiefly lithium light, and index measurements made in such mixtures with white light give nearly the indices for lithium light. SELENIUM AND ARSENIC SELENIDE MELTS. Dr. Merwin 12a has found that mixtures of selenium and arsenic selenide cover the range of indices of refraction from 91^ = 2.72 to 7^ = 3.17. These mixtures melt at rather low temperatures and are generally satisfactory, although they are deeply colored and measure­ ments must be made for red light. Measurements can be made with these mixtures with a probable error of less than 0.02, but only under the most favorable conditions. The mixtures can be made by heating together metallic arsenic and selenium in weighed quantities or by first making As2Se3 and then adding the proper proportion of selenium. Thorough stirring is necessary to insure homogeneous melts. The following table gives the indices of refraction for different wave lengths of light for several mixtures of selenium and arsenic selenide. Indices of refraction for mixtures of selenium and arsenic selenide.

60 per 22.6 per cent Se, cent Se, MM Se. 40 per 77.4 per As2Sea. cent cent AssSea. AszSes.

640 2.78 2.90 660 2.74 2.86 3.06 680 2.71 2.83 3.01 3.17 700 2.68 2.80 2.97 3.13 720 2.66 2.77 2.94 3.10 ' 740 2.64 2.75 2.92 3.07 760 2.62 2.73 2.90 3.05

Dr. Merwin has also informed me that a mixture of 10 per cent tellurium and 90 per cent As2Se3 gives indices of refraction 0.04 higher than the As2Se3 but is almost too opaque to use with an ordi­ nary tungsten lamp. By means of direct sunlight or a "pointolite" lamp even more nearly opaque mixtures can be used.

METHODS OF STANDARDIZING MEDIA FOR MEASURING INDICES OF REFRACTION. A number of methods of standardizing the embedding media by the microscope have been devised,13 but the method that employs the total refractometer or the method of measuring minimum deviation with a prism are much more satisfactory, and with either method accuracy to a few units in the fourth decimal place is easily

wa Merwin, H. E., private communication. The data are preliminary. is Johannsen, Albert, Manual of petrographic methods, pp. 265-270,1914. Wright, F. E., Measurement of the refractive index of a drop of liquid: Washington Acad. Sci. Jour., vol. 4, pp. 269-279,1914. METHODS OF DETEKMINING THE OPTICAL CONSTANTS. 21 attained. The refractometer may yield quicker results than the prism, but it can not be used with media whose indices are greater than about 1.86, and even with reasonable care it may be seriously injured by scratching or by corrosion from some of the liquids. The liquids containing methylene iodide in particular should not be allowed to remain on the hemisphere any longer than is necessary, and liquids from which crystals may separate should not be used, as the crystals may scratch the hemisphere.14 The method of minimum deviation with a prism is not quite so rapid as that with the refractometer, but it can be used for the whole range of embedding media.15 Any hollow prism can be used, but suitable prisms can be quickly made from two optically true glass plates about 5 by 20 millimeters in size.by fusing them together at one corner in a blast lamp, taking care not to bend the glass, so as to form a prism that has nearly the desired angle. About one in a hundred of a good grade of petrographic object glasses is suitable. The glasses can be very quickly tested by watching the reflection on all parts of the glass of a cord in front of a window at a distance of about 10 feet. If the two surfaces are not parallel two reflections will be seen; if they are not plane surfaces, the reflections will be distorted. The unfused end of this prism can be pressed onto a small drop of melted soft glass and a base to the prism thus made. Surface tension will keep the liquids in place. Instead of being mounted on a glass base the prism may be mounted in plaster of Paris coated with dental cement to glaze it. The glass plates should fit closely together, and it is well to cement the contact on the outside with dental cement to make a tight joint. Dr. C. S. Koss 16 has shown that better prisms can be made by grinding a piece of glass to a rough prism of any desired angle by measuring with a contact goniometer, grinding the edges of the two glass plates so that they will fit tightly together, and cementing the glass plates to the prism with bakelite so that a few millimeters of the glass plates will project above the top of the glass prism. The edges of the glass plates are also cemented with bakelite. It is convenient to have the top of the prism slope into the angle between the plates and thus make a tight receptacle for the drop of liquid. A prism angle of about 60° is best for liquids that have moderate indices of refraction. A much smaller prism angle one of 30° or

» For a description of the crystal rcfractometer and its use see Rosenbusch (Wiilfing), Mikroskopische Physiographic, Band 1, Erste Halfte, pp. 218-222, 272-275, 1904. Groth, PhysikalischeKrystallographie, pp. 704-711, 1905. Duparc and Pearce, Traite1 de technique mine'ralogique et piStrographique, pp. 385-392, Leipzig, 1907. 16 For a description of this method see Groth, op. cit., pp. 27, 690-696,1905; Duparc and Pearce, op. cit., pp. 26,369-376, or any textbook on light. M Private communication. 22 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. less must be used for liquids that have high indices of refraction. If a prism is to be used for a series of measurements a curve or a table should be constructed to show the index of refraction corre­ sponding to any angle of minimum deviation. For the mixture of sulphur and selenium, the pipeline preparations, or other solids, the prism can be molded between fragments of cover glass.

MEASUREMENT OF ALL INDICES OF REFRACTION OF CRYSTALS. Most crystals have two (co and e) or three (a, j8, and 7) principal indices of refraction, and for accurate work it is desirable to measure them all. If it is not necessary to measure all of the indices it is best to measure a particular one, preferably /3, as otherwise any value from the lowest to the highest may be measured. If /3 is measured the others can be estimated from the birefringence and the axial angle. The measurements of all the indices of refraction of a mineral can be made very quickly and within the limits of accuracy of the immer­ sion method if the powdered grains show no marked tendency to lie on a particular face or cleavage, as do those of the micas, calcite, and many other minerals. Grams of minerals with such cleavages as the amphiboles, pyroxenes, and feldspars can generally be turned to any orientation without much difficulty. To test the lowest and the highest indices of refraction of such minerals against the embed­ ding media a gram should be chosen that appears to show strong birefringence, both the thickness of the grain and the interference color being taken into account. The grain should be turned to extinction and tested against the embedding medium, then turned t.o the other extinction (or the lower nicol should be revolved 90°) and tested again. This procedure should be repeated on a number of grains, and with a little practice, unless the birefringence is extreme, many of them will show the lowest index of refraction, equal to a, or the highest index equal to 7, within the limits of error of the immersion method. For any grain or any orientation of a crystal plate j3 lies between the highest and the lowest values measured. Therefore /3 can be measured on a gram that shows no measurable birefringence. Such a grain is nearly normal to an optic axis and is suitable for observing the optical character, the size of the axial angle, and the dispersion of the optic axis. If the dispersion is considerable it will give abnormal interference colors without extinction. Uniaxial minerals may be considered simply as a small group of biaxial minerals in which 0 is equal to a for a positive mineral and to 7 for a negative one. The lowest index of every grain of a uniaxial positive mineral and the highest of a uniaxial negative mineral is equal to co and can be measured on any grain. It may be desirable to turn the grain over. This can be done by shifting the cover glass with the point of a pencil. The movement can METHODS OF DETERMINING THE OPTICAL, CONSTANTS. 23

be controlled better with a viscous immersion medium than with one that is very fluid. Small cover glasses are more satisfactory than large ones, as they are much more easily manipulated. A cover glass 11 millimeters in diameter, divided into quarters or even ninths, is most used by the author. By turning and transferring a single small crystal to different media all the optical properties can be measured. Some grains may be conveniently oriented by observing interference iigures. A section normal to the acute bisectrix will give /3 normal to the plane of the optio axes, and in that plane a for 'a positive mineral or 7 for a negative mineral. A section normal to the obtuse bisectrix give /3 and 7 or a; one parallel to the plane of the optic axes gives a and 7. Any section normal to the plane of the optic axes gives /3. Fibrous or prismatic fragments require a somewhat different treatment. If their extinction is nearly or quite parallel they will give one of the principal indices when turned with their length par­ allel to the plane of vibration of the lower niool. The other two indices can be measured across the fibers by measuring a number of fibers, provided the mineral does not persist in lying on a particular face. In that event it may be necessary to roll a fiber, keeping it parallel to the cross hairs, and to observe the maximum or minimum index as it revolves. With a little practice this work can be done easily, unless the mineral is composed of very thin, broad laths. The face or cleavage on which a mineral tends to lie is likely to be normal to one of the principal optical directions. This tendency may be tested by an interference figure. On grains that show this tendency two of the indices of refraction can readily be measured and the other index can be obtained by turning the flake on edge. Monoclinic minerals that are prismatic along (c) or (a) show parallel extinction for prisms that lie on any face parallel to crystal axis 6 and nearly the maximum inclined extinction if turned parallel to the face (010) which is normal to that axis. Prisms that lie on a face parallel to axis b will give for the ray vibrating across the prism the index of refraction (a, /3, or 7) of the ray which vibrates parallel to axis &. Prisms that lie on the face (010) will give the other two indices of refraction and also the extinction angle, X (Y or Z) to c (or a). Triclinic fibers that have inclined extinction are more difficult to measure, but with a little ingenuity measure­ ments can usually be made. The stronger the birefringence, how­ ever, the more accurate must be the orientation to obtain accurate results. Platy minerals, such as mica, are more difficult to manipulate, and if their birefringence is considerable they require skill and patience in order to get good results. Fortunately in nearly all such 24 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. t minerals the rays corresponding to one index vibrate nearly or quite normal to the plate and those corresponding to the other two vibrate in the plane of the plate and can be easily measured. The index normal to the plate can be obtained by turning the plates and keeping them on edge; this can often be done in a viscous liquid or they may be measured as they are turned. It is sometimes help­ ful to mix a little powdered glass with the mineral or to have grains of varying size to separate the cover glass and object glass enough so that the mineral plates can turn over. One of two plates that are differently oriented and attached together may be more easily turned on edge. Many such minerals can be cut with a knife across the plates and the resulting fragments placed on the object glass in the position desired.

MEASUREMENTS OF AXIAL ANGLES. The following methods of estimating or measuring the axial angle of mineral grains have been found most convenient by the author: (1) Observing the curvature of the hyperbola in sections cut nearly normal to an optio axis; (2) measuring or estimating the distance between the hyperbolas on a section cut nearly normal to the acute bisectrix; (3) computing the axial angle from the three indices of refraction.17 All observations are best made on grains immersed in a medium that has an index of refraction approximately equal to that of j8 for the mineral. From the curvature of the hyperbola of an interference figure the axial angle can be measured, under favorable conditions, with an error of ±3°.18 With a little experience a rough estimate can be made by merely inspecting the curvature of the hyperbola. If the bar appears straight, when turned to the 45° position the axial angle is nearly 90° and as the curvature becomes greater the axial angle becomes smaller. More accurate and rapid measurements can be made on sections approximately normal to the acute bisectrix, provided the axial angle is not so large that the hyperbolas are outside the field of the microscope. Measurements of the axial angle in air (2E), by using a cross-grating ocular, can be made on such sections in a few minutes with a probable error of only a few degrees.18 A grain that is not well oriented can commonly be turned by carefully touching the cover glass.

17 For an excellent discussion of measurements of axial angles, see Wright, F. E., The methods of petro- graphic-microscopic research: Carnegie Inst. Washington Pub. 158, pp. 147-200,1911. J8 Wright, F. E., op. cit., pp. 155 et seq. METHODS OF DETERMINING THE OPTICAL CONSTANTS. 25

The axial angle can bo computed from the values of the three indices of refraction according to the formula

JL_i TanJ. UJJ. 2 VV a - ' i

or by the approximate formula 10 Cosx-i 29 Vxr a = 7 a in which 2Va is the axial angle about a. For a discussion of these formulae see page 10. As the error in measuring the indices of refraction by the immersion method is considerable in comparison with the birefringence of most minerals, this method is very rough unless the birefringence is considerable.

DISPERSION OF THE OPTIC AXES. The dispersion formula p > v (or p < v) simply means that the axial angle is greater (or less) for red than for violet light. For rapid work the dispersion can best be observed on an interference figure which shows at least one optic axis well in the field of vision. For orthorhombic minerals or for monoclinic minerals in which the plane of the optic axes contains the crystal axis I both hyperbolas must show the same dispersion, but for other crystals the dispersion may be different for the two optic axes, and to determine definitely the dispersion both optic axes must be taken into account, or, better, the axial angles should be measured for different colors of light. For crystals in which both hyperbolas show the same dispersion, if p < v is moderate the dark hyperbola should show on a sharp interference figure a faint but distinctly perceptible reddish color on the concave side and bluish on the convex side. These borders are reversed if p>v. If the dispersion is strong these borders become pronounced, and many minerals show no dark hyperbola but a series of colored ones. If the dispersion is extreme the interference figure can hardly be recognized in white light.

OPTICAL CHARACTER. The optical character of a mineral can be conveniently determined on grains that show the emergence of the acute bisectrix, the obtuse bisectrix, either of the optic axes, or the optic normal (Y); it can also be determined from the values for the indices of refraction. In making any of the tests it is desirable to have the grains embedded in a medium that has an index of refraction nearly that of the /3 index of refraction of the mineral grain, as otherwise the interference

19 A graphic solution of this equation is given in Wright, F. E., op. cit., pi. 9. 26 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

figure will be distorted. Grains can be turned into the desired position by gently shifting the cover glass. In a viscous liquid, such as Canada balsam, even fibrous or micaceous minerals can readily be turned to any desired orientation. A few grains of powdered glass dusted through the embedding media will raise the cover glass so that the grains or fibers can be turned. Highly viscous liquids like Canada balsam or Peru balsam (n = 1.593) are good media in which to turn fibers on edge. Sections that show the emergence of an optic axis are by far the most serviceable, as they can easily be recognized by their interference colors, which are low to zero, and in minerals that have moderate or strong dispersion are abnormal. Moreover, in such sections the acute and obtuse bisectrices can be distinguished, unless the axial angle is very near 90°. The tests are made in the usual way. The author uses the red of the first order for most tests, but for minerals that are deeply colored, especially if they have very strong birefringence or if the grains are embedded in a deeply colored melt, the quartz wedge is more satisfactory. It is often convenient or even necessary to determine the position of the optic plane and make the test on the grain itself by observing an edge where it wedges out. The tests can be made without a wedge or plate by observing the indices in the two directions against the embedding media, provided it is between the two or near one of them. The optical character can be determined from the indices of refrac­ tion. If /3 a is decidedly greater than 7 /3 the mineral is optically negative; if decidedly less it is positive. (See p. 11.) This relation should be used chiefly as a check on the other data, but for some fibrous minerals whose acute bisectrix is along the fibers it may be the only means of readily determining the optical character. OPTICAL ORIENTATION, DISPERSION OF BISECTRICES, AND CRYSTAL SYSTEM. Crystal habit and prominent cleavage, twinning, and other phe­ nomena may be quickly observed under the microscope and their relations to the optical characters determined. By observing the in­ terference figure the complete optic orientation of any grain, such as one lying on a cleavage or a crystal face, can be roughly made out. This observation is especially suitable for determining the optical position that corresponds to the direction normal to the grain. The orientation in the plane of the section can best be obtained by meas­ uring extinction angles and determining the position of the slow ray and the fast ray by means of a red of the first order or a quartz wedge, or by testing the indices against the embedding medium. The dis­ persion of the bisectrices can be determined by measuring extinction angles in different colors of light. For ordinary purposes it is suffi­ cient to observe the color phenomena in ordinary daylight when the METHODS OF DETERMINING THE OPTICAL CONSTANTS. 27 crystal is near extinction. If the dispersion is slight the extinction should be sharp; if considerable there will be no sharp extinction but abnormal interference colors over a range depending on the extent of the dispersion. It is commonly possible to determine the crystal system to which a mineral belongs from the microscopic study. The fact that min­ erals such as biotite may be sensibly uniaxial or may give sensibly parallel extinction introduces some uncertainty. Isotropic minerals are amorphous or isometric. Uniaxial minerals are tetragonal or hexagonal. Biaxial minerals with parallel or sym­ metrical extinction are orthorhombic. Biaxial minerals with inclined extinction for fragments normal to one principal optical direction and parallel or symmetrical for those normal to the plane of the other two are monoclinic. Biaxial minerals with inclined or unsym- motrical extinction for all orientations are triolinic. Monoclinic minerals elongated in the direction of crystal axes a or c can be conveniently examined by rolling the fragments. When such fragments are turned so as to give parallel extinction crystal axis 6 and one principal optical direction lie across the length. 'When the fragments lie on a face normal to crystal axis 6 they should show approximately the maximum extinction angle. In the conoscope an interference figure should also appear in the canter of the field of the microscope. Such sections will give the characteristic extinc­ tion angle X (Y or Z) Ac (or a). Pleochroism can be conveniently observed at the same time.

OTHER TESTS. The optical properties are sufficient for the accurate determination of most minerals, but the occurrence and association of the mineral should be considered, a macroscopic examination made, and such simple properties as hardness noticed. It may be desirable also to determine the fusibility and the,specific gravity or to make simple chemical tests. Microchemical examinations have not received the .attention from mineralogists that they deserve. CHAPTER III. SOME STATISTICS ON THE OPTICAL PROPERTIES OF MINERALS.

DISTRIBUTION OF MINERALS WITH REGARD TO OPTICAL CHARACTER. The tables in Chapter IV contain data for about 950 mineral species, but some species appear more than once, and there are about 1,200 entries. They are distributed as follows: Per cent. Per cent. Isotropic...... 16.1 Biaxial+...... 28. 9 Uniaxial-f-...... 7.7 Biaxial ...... 30. 0 Uniaxial ...... 13. 5 Optical character unknown...... 3. 8 Many of the isotropic minerals are amorphous and some minerals that are placed under the uniaxial groups are strictly biaxial but have small axial angles or their apparent uniaxial character is due to aggregate polarization of fibers or lamellae. A few of those included in the biaxial groups are uniaxial and appear biaxial on account of strain. The small number of uniaxial positive minerals as compared with uniaxial negative minerals is noteworthy.

DISTRIBUTION OF MINERALS WITH REGARD TO INDEX OF REFRACTION AND BIREFRINGENCE. The distribution of the minerals with regard to their intermediate index of refraction /3 is shown in figure 4. For only 10 minerals, or less than 1 per cent of the total number, is /3 less than 1.400, and for only about 28, or about 2 per cent, is 0 greater than 2.70. For about 54 per cent of all the minerals /3 is between 1.475 and 1.700. The distribution of the minerals with respect to their birefringence is shown in figure 5. Curve 1 shows that the greater number of the minerals have a birefringence of about 0.018 and that the number rapidly decreases on both sides of this value. Curves 2 to 5 show the distribution as regards birefringence of the minerals whose indices of refraction /3 lie between certain values. The greater number of minerals in which /3 is lower than 1.80 have birefringence of about 0.015. For minerals in which /3 lies between 1.80 and 2.00 the greatest density of distribution is for a birefringence of about 0.035, and for those in which 0 is greater than 2.00 there is no marked maximum for the curve. These curves show a striking tendency for minerals which have high indices of refraction to have also strong birefringence. This tendency is equally well shown by the per- 28 DENSITY OF DISTRIBUTION 0) Co > * to

o rn o tJ x 2. °

£0p - 5 a > o o Q d d 30 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. centage distribution of minerals which have birefringence greater than 0.20. Per cent. Per cent. /3 less than 1.80...... 1 18 between 2.2 and 2.6...... 10 P between 1.80 and 2.0...... 11 /3 greater than 2.6...... 48 0 between 2.0 and 2.2...... 14

RELATION BETWEEN INDEX OF REFRACTION, DENSITY, AND CHEMICAL COMPOSITION. Gladstone and Dale long ago showed that Every liquid has a specific refractive energy composed of the specific refractive energies of its component elements, modified by the manner of combination, and which is unaffected by changes of temperature and accompanies it when mixed with other liquids. The product of this specific refractive energy and the density is, when added to unity, the refractive index.20 Or, where K is the specific refractive energy of any substance and &i> &2> p1} p2, etc., are the specific refractive energies and the weight percentages of the components of that substance. These components- may be the elements or radicals that enter into a compound or the constituents of a solution. In general these relations hold rather accurately for varying temperature, pressure, and concentration in liquids and gasses, but when applied to a substance in a different state as liquid and gas the formula gives errors as great as 30 per cent. On the basis of the electromagnetic theory of light Lorentz ^2 _ ^ ^ and Lorenz independently derived the formula 2 0 -j = k. This vti -p Z Cu formula holds somewhat better for substances in a different state but nevertheless gives a considerable error. Moreover, some substances, as oxygen in some organic compounds, have two or more specific refractive energies, depending on the structure of the molecule. When Gladstone's law is applied to crystalline substances the mean index of refraction K or 5 must be used and the 6 o relations hold only approximately. The formula yco2e or -\/

20 Gladstone, J. H., and Dale, T. P., Researches on the refraction, dispersion, and sensitiveness of liquids: Roy. Soc. London Philos. Trans., vol. 153, p. 337,1864. SOME STATISTICS ON THE OPTICAL PROPERTIES. 31 of refraction are available may be imperfectly known. However, the values shown in Table 2 for the specific refractive energies ( ^ =kj of the chief constituents of minerals have been com­ puted by taking the average as derived from a number of minerals for which the available data seemed fairly reliable.

TABLE 2. Specific refractive energies ~~

Molecular Jr. Molecular weight. weight. /;.

H.O...... 18 o 0.335.'., AssOa...... 198 (70.202,^0.225 6.340, O54~ YtiO...... 90fi 144 Li20...... 30 .31 Sbs03...... 228.4 a 9flQ rf ooo (NHOaO...... 52 .503 149 Na20...... 62 .181 Ce203...... KjO...... 94 .189 Bia03...... 464 .163 CuiO...... 143 .250 C0j...... 44 .217 Rb20...... 187 .129 SiOj...... fifl .207 AgjO...... 232 .154 TiO2...... on 397 Cs20...... 282 .124 SeO2...... 111 .147 HgaO...... 416 .169LI ZrO«...... m e .201 TlaO...... 424 .120 8nQ3 ...... 111 14^ G1O...... 25 .238 SbOs...... 1 ^9 .198 MgO...... 40.4 .200 TeOj...... 159.5 e. 200L| CaO...... 56 .225 Th02...... 264.5 19 MnO...... 71

a Water and ice. / Calculated from feldspar, feldspathoids, etc. 6 Average. g Isometric oxide. c Alums, etc. A Monoclinic oxide. d Calculated from compounds containing the oxide. < Orthorhombic oxide. «Calculated from the oxide.

Atomic Atomic weight. k. weight. fc.

H...... 1 1. 256 or 1. 44 S...... 32 J0.502, * 1.00 c...... 12 .403 Cl...... 35.5 sni 0...... 16 .203 Br...... 80 .214 F...... 19 .043 I...... 127 .226

i Calculated from native sulphur. * Calculated from sulphides; values vary. These values are only approximate, but in a number of minerals selected at random the value of Jfc as computed from n and d and as computed from that of its constituents agreed with few exceptions within o per cent. A very few minerals show a much greater difference. 32 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

As shown in the table for most radicals, the value of fc is near 0.20. For S, (NH4)A Ti02, Te03; and V205 it is higher, and for Cs2O, BaO; PbO, Th02, U03, and F it is much lower. There is a tendency for the value of k in each group to decrease as the molecular weight increases, but there are many exceptions. The \alues of fc for BaO, SrO, and CaO show why related minerals of these three oxides have about the same indices of refraction but very different densi­ ties. The values for Cb205 and Ta205 show why the columbates commonly have higher indices of refraction but lower densities than the corresponding tantalates. The extremely low value for fluorine accounts for the remarkably low indices of refraction and comparatively high densities of the fluorides. Minerals containing any of the following radicals as essential con­ stituents are likely to show strong dispersion: (NH4)02, N2O5, U03, Sb205, AsA, P305, VA, FeA, Mn203, Mo03, or Ti02. CHAPTER IV. MEASUREMENTS OF OPTICAL PROPERTIES OP MINERALS. COMPLETENESS AND ACCTJKACY OF THE DATA. Out of about 950 species included in the tables suitable data were available for only about 400 species, and the author found it necessary to measure some or all of the optical constants of over 500 species. With these new measurements fairly satisfactory optic constants are available for all the minerals in the tables except armangite, atopite (Norway), boothite, cappelenite, carminite, catop- tritc, georgiadesite, hellendite, hieratite, jeremejevite, manandonite, monimolite, morinite, nordenskioeldine, palmerite, phoenochroite, rhagite, rivaite, uhligite, and vrbaite, specimens of which the author was unable to find, and the unstable minerals dolerophanite, erythro- siderite, hydrocyanite, ilesite, kremersite, mallardite, molysite, old- hamite, and scacchito. It is hoped that data for these will soon be available and that hereafter descriptions of new minerals will include the optical constants; indebd, no mineral description is ade­ quate without them. "With few exceptions the measurements were made by the methods described in the preceding chapter. The probable maximum limits of error are stated, but in some minerals the error may be considerably greater, for not all the measurements have been made twice. In many minerals the optical orientation in particular is only approxi­ mate and incomplete, for faceted crystals were rarely available. The powdered fragments were observed under the microscope for cleavage, elongation, or other easily recognized crystal direction, and the optical orientation was determined with relation to these features. The greatest difficulty in procuring the data has been to get cor­ rectly labeled specimens, and much labor has been expended in getting consistent results. If type material had been available for all the minerals the results would be much more valuable and much labor would have been saved. So many errors in labeling specimens have been discovered that possibly a few of these errors have escaped detection. However, where there was any doubt as to the identification of the species a number of specimens were examined and on a few of the species, where sufficient material was available, simple chemical tests were made. The species that caused the most difficulty in these respects were the amorphous and microcrystalline minerals the so-called colloids and meta- 12097° 21 3 33 34 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

colloids and a few groups like the chlorites, the ferric sulphates, and the secondary uranium minerals. The data on some of these species will not be entirely satisfactory until the chemical analyses and optical measurements are made from identical material. The measurements have brought out a number of valuable inci­ dental results, among which are the following: Priceite is a distinct species. There is a remarkable series of amorphous hydrous oxides of antimony and some crystalline varieties that need much more study. Mazapilite is identical with arseniosiderite. Both forms of PbO massicot and litharge exist in nature. A number of the colloidal minerals are variable and are hardly entitled to be called species. Some of the metalloidal minerals may not be homogeneous. Chemical analyses of such material without careful microscopic examination are well-nigh useless. Liebigite is probably identical with uranothallite. Partschinite is probably identical with spessartite. Much allanite is made up of a perceptibly isotropic form and a strongly birefracting form that is derived from the isotropic form. The material commonly identified as scorodite is highly variable and needs further study. Bementite and cafyopilite are identical. THE NEW DATA. In the following pages of new data the species are arranged in alphabetical order, except where it was desired to show relations, and to these minerals cross references are given. The data are pre­ sented as briefly as possible, and discussions and references to the literature are avoided as far as practicable. Under each mineral description the locality is named first, and the source of the specimen is placed next in parenthesis. The descrip­ tion of the hand specimen follows, if it is deemed essential, and after that the optical properties are given as determined on the powder. The greater part of the material was obtained from the following collections: Abbreviation. Col. Washington A. Roebling...... Col. Roebling. United States National Museum...... U. S. N. M. American Museum of Natural History...... A. M. N. H. University of California...... U. of C. Yale University...... Yale. Harvard University...... Harvard. California State Mining Bureau...... Cal. Min. Princeton University...... Princeton. Johns Hopkins University...... J. H. U. Mr. F. A. Canfield, Dover, N. J. MEASUREMENTS OF OPTICAL PROPERTIES. 35

Mr. Frank L. Hess, Washington. D. C. Dr. W. T. Schaller, Washington, D. C. Mr. R. M. Wilke, Palo Alto, Calif. Field Museum of Natural History...... F. M. N. H. Chicago. University of Stockholm...... U. of Stockholm. National Museum of Natural History, Stockholm.N. M. N. H. Stockholm.

ACMITE. Kongsberg,-Norway (U. S. N. M. 16568). Optically-, 2V = 66°±5° (indices). a = 1.765±0.003. 0 = 1.803 ±0.003. y = 1.820 ±0.003. These data are near those of Wiilfing for aegirite from Langesund: a = 1.7630 0 = 1.7990 7 = 1-8126

ADAMITE. Laurium, Greece (U. S. N. M. 50164). Nearly colorless, drusy crystals. Optically-, 2V = 87°±5° (indices). p>v (strong). Z is parallel to the elongation of the fragments. a =1.708 ±0.003. 0 = 1.734 ±0.003. 7 = 1.758±0.003. It may be in part optically + and p

ADELITE. 1. Jacobsberg, Sweden (N. M. N. H. Stockholm). Yellow or brown, greasy aggregates. Optically+, 2V nearly 90°, p adelite. Brownish grains embedded in a large amount of hedaphane. The brownish grains have the following optical properties: Optically + ,, 2V = 61 ° ±5° (indices), p

AENJGMATITE. See Enigmatite. AESCHYNITE. See Eschynite. AGRICOLITE. 1. Johanngeorgenstadt, Saxony (Harvard). Lemon-yellow, coarsely radiating crystals. 2V large (?). Optically +, birefringence very low. 0=1.99±0.01. 36 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

There is also a finely fibrous mineral, probably an alteration product of the agricolite. 2. Schwarzenberg, Saxony (A. M. N.-H.). A finely fibrous min­ eral with moderate birefringence. . 0 = 2.03 ±0.01. Probably an alteration product.

ALABANDITE. La Sheeha, Puebla, Mexico (U. S. N. M.). Translucent and isotropic. ?iLi = 2.70±0.02.

ALLACTITE. Nordmark, Sweden (A. M. N. H.). Optically , 2V very small, p>v (very strong). a = 1.761 ±0.003. /3= 1,786 ±0.003. 7 = 1.787 ±0.003. Colorless in powder. ALLANITE. 1. Crest of Blue Ridge, 9 miles south of Roanoke, Va. (Prof. T. L. Watson). A microscopic study of the black vitreous allanite-, ap­ parently from the freshest part of the specimen, showed that it is made up of two different minerals, a pale olive-green, sensibly isotropic mineral and a pale-green birefracting mineral. The bire- fracting mineral is derived from the sensibly isotropic mineral and replaces it along streaks and irregularly. The isotropic mineral has an index of refraction of about 1.697 ± 0.003. The birefracting mineral is faintly pleochroic; X = pale green and Z = yellowish. The mean index of refraction is about 1.71 and the birefringence is about 0.01. 2. Amherst County, Va. (F. L. Hess). All the material examined is birefracting. It is probably optically negative, with a large axial angle, but no good interference figure was obtained, probably owing to some abnormal dispersion. /3 = 1.755 ±0.01. Birefringence = 0.01 approximately. Pleochroic; X = pale yel­ lowish and Z = deep reddish brown. 3. Albany, Wyo. (F. L. Hess). The blackish-brown vitreous material is made up of two or probably three distinct minerals. Thin sections show the relations clearly. A nearly colorless, iso- MEASUREMENTS OF OPTICAL PROPERTIES. 37

tropic mineral is replaced in irregular areas by a pale-greenish, faintly birefracting mineral, and these two minerals are in turn altered along the borders of the grains and along cracks and streaks to a reddish-brown, rather strongly birefracting mineral, which makes up more than half the sections of the large piece and all but a small core of the small grains, some of which are as much as several millimeters across. The alterations suggest the alteration of olivine to iddingsite, and in both the oxidation of iron is probably an important change. a. The colorless to pale-greenish isotropic mineral has a rather constant index of refraction of 1.685 ±0.005. 6. The pale-green birefracting mineral has a somewhat higher index of refraction and a weak birefringence. It is pleochroic; X = nearly colorless and Z = pale green. c. The reddish-brown mineral has the following optical properties, which vary a little: Optically , 2V = rather large, p>v (rather strong). a =1.727 ±0.005. X = pale yellowish. |8 = 1.739 ± 0.005. Y = reddish brown. 7 = 1.751 ±0.005. Z = reddish brown. 4. Llano County, Tex. (U. S. N. M. 84416). In mass, black and vitreous; in thin section rather deep olive-green. Isotropic and nearly homogeneous. n = 1.725 ±0.005. 5. Garto, Arendal, Norway (U. S. N. M. 49022). Pale olive- green in section and perceptibly isotropic for the fresh vitreous center of the specimen. n = 1.670±0.005; varies somewhat. Much of this specimen is a brownish vitreous alteration product. It is red-brown in section and different grains differ greatly in optical properties. Part is isotropic and part is birefracting. The index of refraction differs greatly but in much of the material it is near 1.60 ±. Evidently the "allanite" of all these specimens is made up of at least two and probably three distinct minerals. One of them is pale, sensibly isotropic, and has an index of refraction of about 1.68 to 1.70; another, possibly related to the one just mentioned, has a somewhat higher index of refraction, a weak birefringence, and is v pleochroic in green and yellow; the third is clearly derived from the others and has the following optical properties: Optically , 2V = rather large, p > v (rather strong). 18=1.71 to 1.76. 38 MICEOSCOPIC DETERMINATION OF NONOPAQUE MINERALS. Birefringence 0.01 to 0.02. Pleochroic in red-brown, with absorp­ tion Y andZ>X. ALUMIAN. Sierra Almagrera, Spain (A. M. N. H.). Minute rhombs that have striated sides, resembling somewhat the hopper-shaped cubes of halite, but they are probably striated rather than skeleton crystals. They show extinction in segments somewhat like hour-glass struc­ ture. When turned on edge they give a good interference figure and are uniaxial +. « = 1.583 ±0.003. e = l.602 ±0.003.

ALUMINITE. 1. Newhaven, Sussex, England (U. S. N. M. 9290). White porcelain-like. Under the microscope it is seen to occur in rather coarse fibers which have negative elongation and perceptibly parallel extinction. 2V very near. 90°. a = 1.459 ±0.003. /3 = 1.464 ±0.003. 7 = 1.470 ±0.003. 2. Near Denver & Rio Grande Railroad at crossing of Green River, Utah (H. S. Gale). A white, chalky nodule. The main part is nearly pure aluminite, but the surface is largely composed of another mineral, probably a dehydration product of the aluminite. The aluminite occurs in minute prisms which have perceptibly parallel extinction and X parallel to the elongation. Optically + , 2V large. a = 1.460 ±0.003. 7 = 1.470 ±0.003. The dehydration product occurs also in prisms, probably after the aluminite. It shows large extinction angles, is optically +, and has a large axial angle. An optic axis emerges nearly normal to the prisms. 0 = 1.500 ±0.003. Birefringence 0.01. 3. Saxony, Germany (U. S. N. M. 16793). Earthy white mass. Very finely fibrous, probably optically +. j8 = 1.52±0.01. Birefringence about 0.02. Not very satisfactory and rather doubtful; may be the alteration product of specimen 2. ALUNOGEN. 1. South Bolivia (U. of C.). White fibers that have a large extinction angle. Optically 4-. « = 1.475±0.003. 0 = 1.478 ±0.003. 7 = 1.485±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 39 2. Utah (U. S. N. M. 47550). White fibers with extinction angles from 0 to very large. Angle of Z to elongation large. Optically+, 2V small. a = 1.473±0.003. ft = 1.474±0.003. 7 = 1.480±0.003. ' Probably monoclinic1. ALURGITE. Piedmont, Italy (W. T. Schaller). Copper-red mica. Optically , 2V near 0, p>v (slight). j8 = 1.594±0.003. Birefringence near that of muscovite. In thin flakes; pale pinkish; pleochroism very faint. AMAKANTITE. Caracoles, Chile (U. S. N. M. 82631). Minute fibers. Optically -, 2V = 28°±5° (indices), pleochroic with absorption Z> Y»X. a = 1.51 ±0.01; nearly colorless. j8 = 1.605 ±0.003; pale orange- yellow. T = 1.611 ±0.003; orange-yellow. /''

AMPANGABEITE. Ampangab6, Madagascar (Col. Roebling). In section red-brown and isotropic. Fracture conchoidal. n = 2.13 ±0.03.

ANAPAITE. Anapa, Russia. Soft, glassy, greenish-white crystals. Opti­ cally + , 2E = 94°±3° (measured), 2V = 54°±2°, P >v (perceptible). a = 1.602 ±0.003. j8 = 1.613 ±0.003. 7 = 1-649 ±0.003. Some plates are nearly normal to Z. Sachs 21 states that the mineral is optically . 2H = 127° (n= 1.5753) p v.

ANCYLITE. Narsarsuk, Greenland (U. S. N. M. 84875). Brown crystals. Pale green in section. Optically +, nearly- or quite uniaxial. o> = 1.865, somewhat variable. Birefringence about 0.04.

» Sachs, A., Akad. Wiss. Berlin Sitzungsber., 1902, p. 18. 40 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

ANDRADITE. Arizona (analyzed by W. T. Schaller). Empire mine, Nogales quadrangle, Ariz. The analysis 22 gives Si02, 37.16; A1203, 3.47; Fe203, 28.11; CaO, 30.23; MgO, 0.51; FeO, none; MnO, present. n = 1.890±0.005 (varies Q.01).

ANKERITE. 1. Antwerp, N. Y. (U. S. N. M. 44870). Light-brownish rhombs. Not homogeneous. Uniaxial . co ranges from less than 1.73 to greater than 1.83. The greater part has co about 1.83. 2. Chester County, Pa. (U. S. N. M. 3965). Nearly colorless cleavage pieces. Uniaxial . co ranges from 1.705 to 1.715. Birefringence as in calcite.

ANNA^ERGITE. Lovelocks, Nev. (U. of C.). Tabular crystals with elongated, rhombic outline (fig. 6). The angle between the edges is 55° ±1°. The crys­ tals are zoned. The main part of the crystals has the following optical properties: Optically -, 2V-82°±3° (indices), p>v (rather strong). Nearly colorless in section. X is sensibly nor­ mal to the tablets, Y is in the acute angle of the rhombs and makes an angle of 35%°±%° with the longer edge. There appears to be a perfect cleavage parallel to the flat face and possibly to the two other faces. FIGUBE 6. Optical orientation and zonal growths of anna- to = 1.622 ±0.003. (3 = 1.658 ±0.003. bergite on tabular face {010>. 7 = 1.687±0.003. A narrow outer zone has a considerably lower index of refraction and a larger extinction angle. It probably contains magnesium and is related to cabrerite. Annabergite must be monoclinic, and X = &, ZAe = 35£° in acute angle j3 (variable). ANTLERITE. Arizona (original material, U. S. N. M.). Optically + , 2ENa = 62°±5° (measured), 2VNa = 35°±3 0 , p

S. Geol. Survey Bull. 582, p. 83, 1915. MEASUREMENTS OF OPTICAL PROPERTIES. 41 elongation; the plane of the optic axis is normal 'to the fibers, pleo- chroism is strong, absorption Y^Z>X. a = 1.730 ±0.003; pale yellow-green (31/).23 0 = 1.737 ±0.003; viridine green (33d).23 7 = 1.785 ± 0.003 ; viridine green (33e).23

APHROSIDERITE. 1. Weilburg, Prussia (Yale, B. Coll. 3904). Chiefly minute fibers with some hexagonal plates. These plates are perceptibly isotropic. a and j8 = 1.612 ± 0.003 ; olive-green. 7 = 1.616 ± 0.003 ; colorless. The plates gave no satisfactory interference figure, but they are evidently optically+ and have a small axial angle. 2. Nassau (A. M. N. H.). Plates and fibers. Optically , 2V=amall. Tend to be on a face normal to a = 1.58±0.01, 7 = 1.60±0.01. The properties ar/ variable and the mineral doubtful. 3. British Columbia. Very finely crystalline. 0 = 1.623 ±0.003. Birefringence low. APJOHNITE. " Bushmanite," Baschjesman Rio, South Africa (Col. Roebling). Soft, white, silky fibers. Optically , 2V small. Sections normal to the plane of the optic axis show parallel extinction, sections par­ allel to that plane show large extinction angles, ZA elongation about 29°. Fibers tend to lie on (010) and to a less extent on (100). Monoclinic ; Y = & and Z A c = 29 ± . a = 1.478 ± 0.003. 0 = 1.482 ± 0.003. 7 = 1-482 ± 0.003.

ARIZONITE. Near Hackberry, Ariz. Original material (U. S. N. M.). Nearly opaque. nu = 2.62 nearly. Birefringence moderate (?).

ARSENIOPLEITE. Sjo mine, Grythytte parish, Sweden (U. S. N. M. 85101). Opti­ cally + , 2V small but distinctly biaxial. Color in transmitted light apricot-orange (II 7 ), nonpleochroic. « = 1.794 ±0.003. e = l. 803 ±0.003.

» Ridgway, Robert, Color standards and nomenclature, 1912. 42 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

AKSENIOSIDEEITE. 1. RomanSche, France (U. S. N. M. 84358). Coating of yellow- brown fibers. Uniaxial . Rather strongly pleochroic in brownish red with absorption «>e. In fibers with the flat face (001) and the optic axis normal to this face and the fibers. co = 1.870 ±0.005. e = 1.792 ±0.005. It may be orthorhombic with a very small axial angle or tetragonal. 2. Jesus Maria mine, Mazapila, Mexico (U. S. N. M. 85174). "Mazapilite." Uniaxial ; strongly pleochroic. co = 1.898 ±0.005, dark reddish brown. e = 1.815 ±0.005, nearly colorless.

ARTINITE. Val Laterna (U. S, N. M.). White fibers. Optically-, 2V = 71° (indices). Y = fibers. The fibers tend to lie on a face nearly normal to an optic axis. a =1.489 ±0.003. 0 = 1.534 ±0.003. 7 = 1.557 ±0.003.

P ASCHARITE. Schmidtmannshall, Prussia (Col. Roebling). Very minute, matted fibers, X = elongation. a=1.53 0=1.55 7 = 1.55 All three values somewhat variable. Evidently optically with small 2V.

ASTRO-LITE. Neumark, Germany (A. M. N. H.). Plates and fibers. Optically , 2V small, p > v (perceptible). X is normal to the plates. « = 1.570±0.003. 0 = 1.594 ±0.003. 7 = 1.597±0.003.

ATELESTITE. Schneeberg, Saxony (Col. Roebling). Optically-H, 2ENa = 107°, 2VNa = 44°±20 (measured), p

AUERLITE. Henderson County, N. C. (U. S. N. M. 4914a). Uniaxial +. 0 = 1.65±0.01. Birefringence 0.01. MEASUREMENTS OF OPTICAL PROPERTIES. 43

AURICHALCITE. 1. Leadville, Colo. Optically , 2V small. The plane of the optic axes is parallel to the cleavage (100), and Z is parallel to the elongation. a = 1.655 ±0.003. 7 = 1.745 ±0.003. 2. Yankee mine, Tintic, Utah (U. S. N. M. 87824). Nearly color­ less plates. Optically , 2V very small, pX. Y is nearly normal to the plates, and Z is parallel to the elongation. a= 1.654 ±0.003. 0= 1.740 ±0.005. 7 = 1-743 ±0.003.

AZURITE. 1. Broken Hill, Australia. Optically+, 2V moderately large, p > v (rather strong). Pleochroic in blue with absorption Z»Y>X. a =1.730 ±0.005. /3 =1.754 ±0.005. 7 = 1.836 ±0.005. 2. Rochester mining district, Nev. Characters similar to those of No. 1. Z normal to cleavage or platy structure. a = 1.730±0.005. /3 = 1.755 ±0.005. 7 = 1.835 ±0.005.

BABINGTONITE. ' 1. Arendal, Norway (U. S. N. M. 47035). Optically+. Disper­ sion strong p > v, 2V medium large, dispersion of bisectrices strong. a = 1.713 ±0.003; deep green. £ = 1.725 ± 0.003; pale brown. 7 = 1.746 ± 0.003; rather pale brown. 2. Baveno, Italy. c a = 1.713 ±0.003. ft = 1.727 ±0.003. 7 =1.746 ±0.003. Otherwise similar to specimen 1.

BADDELEYITE. Minas Geraes, Brazil (U. S. N. M. 86106). Brown grains. Color­ less in powder. Optically-, 2E = 70, 2V = 30±1° (measured), p > v (rather strong). Polysynthetic twinning is common. a = 2.13±0.01. /3 = 2.19±0.01. 7 = 2.20±0.01.

BAKEKITE. Death Valley, Calif. (Harvard). Very fine crystalline aggregates. n = 1.583 ±0.005. Birefringence = 0.02±. Compare with Howlite (p. 87). 44 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

BARRANDITE. 1. Near Pribram, Bohemia (U. S. N. M. 84615). Spheroidal concretions. Fibrous. Optically+ , 2V large, p>v (strong). 18 = 1.65 ±0.03. Birefringence = 0.03 ±. 2. Cerhovic, Bohemia (U. S. N. M. 84343). Pale-yellow crusts. Moderately coarse fibers. Optically + , 2V rather, large, p>v (rather strong). a = 1.535 ±0.003. 0 = 1.541 ±0.003. 7 = 1.554 ±0.003. Probably not barrandite.

BARTH1TE. Guchab, Otavi, German Southwest Africa (Col. Roebling). Grass- green drusy crystals. The microscope shows that they are made up of successive zones. The center and somewhat larger part is very pale green. A rather sharply separated outer shell is much darker and is yellowish green. A. The pale-green core is optically+ , 2V = moderate, p>v (slight to moderate). a = 1.770 ±0.003. 7 = 1.783 ±0.003. « B. The darker, outer zone is slightly pleochroic, optically ±, 2V = near 90°, p

BARYSILITE. Harstig mine, Pajsberg, Sweden (U. S. N. M. 62747). Uniaxial -. co = 2.07 ±0.01. c = 2.05 ±0.01.

BASTNAESITE. West Cheyenne Canyon, El Paso County, Colo. (U. S. N. M. 81857). Uniaxial +. Nearly colorless in section. co = 1.717±0.003. e=1.818±0.003.

BAVENITE. Baveno, Italy (U. S. N. M. 85180). Clear, tabular crystals. Optically+ , 2V small, tablets {100} are nearly normal to X, and Y is parallel to the elongation. Tablets turned on edge show twinning {100} and very small extinction angles. a = 1.578±0.003. j3= 1.579 ±0.003. 7= 1.583 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 45

BAYLDONITE. Near St. Day, Cornwall, England (Col. Roebling). Interwoven fibers too fine for accurate measurements. Optically+, 2V large, p

BEAVERITE. Horn Silver mine, near Frisco, Beaver County, Utah. Type material (U. S. N. M. 86986). Very finely crystalline. Consists in part of minute hexagonal plates. Optically . w = 1.83 to 1.87. Average about 1.85. Birefringence strong. BECHILITE. Bechilite is a doubtful species. The following data are derived from specimens labeled bechilite. 1. Larderello, Italy. Made up chiefly of sassolite and larderellite. 2. Larderello, Italy (A. M. N. H.). Optically+ , 2V = 62° ±5° (indices). Dispersion slight. a = 1.470 ±0.003. 0 = 1.488 ±0.003. 7 = 1.542±0.003. 3. Tarapaca, Chile (J. H. U.). Borocalcite (hayesine). The specimen is no doubt ulexite. 4. See Boussingaultite No. 1 (p. 50). 5. Banos del Toro, Chile (Phillips). Hayesine. Consists partly of minute fibers, in which the angle of Y to the elongation is about 20° and X is normal to the fibers. /3 = 1.509. Birefringence = 0.01 ±. No doubt ulexite. Also a mineral, uni axial . w = 1.531 ±0.003. e = 1.510 ±0.003.

BELLITE. Magnet mine, Tasmania (Col. Roebling). Reddish needles. Nearly colorless in section. Uniaxial . In thick sections faintly pleochroic in pale pink. Absorption « >e. w = 2.16±0.01. e = 2.14±0.01. Probably hexagonal prisms striated parallel to the base and with the base. 46 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

BEMENTITE.

1. Trotter mine, Franklin Furnace, N. J. (U. S. N. M. 47684). Col­ orless shreds and fibers. Optically , 2V nearly or quite 0. X is perceptibly normal to the plates. Resembles sericite. a = 1.624±0.003. j8 and 7 = 1.650±0.003. 2. Pajsberg, Sweden (A. M. N. H.). Caryopilite. Perceptibly uniaxial, optically . Weakly pleochroic in brown, absorption Z >X. The mineral is fibrous and X is normal to the fibers. a =1.602 ±0.003. j3 = 1.632 ±0.003. 7 = 1.632 ±0.003. 3. Harstig mine, Pajsberg, Sweden (U. S. N. M. 85170). Caryopi­ lite. Perceptibly uniaxial (or 2V nearly 0). Optically , fibers- tend to lie on a face nearly normal to X. a = 1.603 ±0.003. |8 = 1.632 ±0.003. 7 = 1.632 ±0.003. The chemical composition, habit, and optical properties of bemen- tite and caryopilite are so much alike as to leave little doubt of their identity. The name bementite has the priority.

BERAUNITE. Giessen, Germany (U. S. N. M. 80622). Variety eleonorite. Optically +, 2V medium large, p > v (very marked). X emerges from the cleavage. Z = &, Y A c = 1.5°. Pleochroic. a = 1.775 ±0.003; pale flesh color (7' f) to colorless. |8 = 1.786 ± 0.003; pale flesh color (T f) to colorless. 7 = 1.815±0.003; carnelianred (7'-) to vinaceous (T i).24

BERZELIITE. Langban, Sweden (U. S. N. M. 48976). Isotropic, clear, and glassy. 7i = 1.727±0.003.

BETAFITE. 1. Antaifasy, Madagascar (U. S. Geol. Survey; from Prof. La- croix). Crystals showing nearly black, glassy center and dull gray, altered outer zones. In section nearly colorless isotropic grains. w=1.915±0.02. 2. Betafo, Madagascar (U. S. N. M.). Similar to No. 1. w = 1.925±0.01.

H Ridgway, Robert, Color standards and nomenclature, 1912. MEASUREMENTS OF OPTICAL PROPERTIES. 47

BEUDANTITE. Dernbach, Hessen-Nassau, Germany (U. S. N. M. 84613). Opti­ cally , 2V medium, abnormal dispersion. Nearly colorless in sec­ tion. /3 = 1.96±0.01. The birefringence is low and gives abnormal green interference colors. The basal hexagonal section is divided into hexagonal segments, and these show polysynthetic twin lamellae parallel to the hexagonal edge. The mineral alters to a brown mineral that has a higher index of refraction, first becoming strongly pleochroic with X' dark brown, and Z' nearly colorless.

BIEBERITE. 1. Artificial bieberite, crystallized from a solution of cobalt sulphate at 23° C. Carmine-colored tabular crystals. Optically ; 2V near 90°; dispersion slight. a = 1.477 ±0.003. 0=1.483 ±0.003. 7 = 1-489 ±0.003. 2. Natural bieberite from Bieber, Hesse; had altered to the pentahydrate corresponding to chalcanthite.

BINDHEIMITE. 1. Fresno County, Calif. (U. of C.). Green, opal-like. In large part isotropic. n=1.84±0.02. The specimen contains a considerable amount of an unknown mineral which probably represents a partial crystallization of the bindheimite and has the following properties: Uniaxial , colorless in section. Perfect cleavage parallel to the optic axis. w = 2.08±0.01. e=1.82±0.01. 2. Fresno County, Calif. (U. of C.). Similar to specimen No. 1 but has a duller luster. n of isotropic part = 1.85 ±0.02. 3. Fresno County, Calif. (U. of C.). Brown, opal-like. Isotropic.. n = 1.87 ±0.01. 4. Locality unknown. Chiefly cryptocrystalline. ?i = 2.0 approximately. 48 MICKOSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

Birefringence strong. 5. Eureka district, Nev. (Cal. Min.). Chiefly isotropic. TJ, = 1.87 ±0.01. Contains also the crystalline mineral of specimen No. 1.

BISBEEITE. Bisbee, Ariz. (original material, W. T. Schaller). Nearly white, cotton-like. Very thin tablets normal to X and with Z parallel to the elongation. Optically+, 2V small, pleochroic. a = 1.615±0.01; nearly colorless. 0 = 1.625 ±0.01; nearly color­ less. 7 = 1.71 ± 0.01; pale greenish. BISMITE. 1. Schneeberg, Saxony (U. of C. No. 597). Canary-yellow powder made up of minute fibers and shreds. a = 1.82±0.02. 7 = 2.00±0.02. The highest index of all the fibers is about 2.00, and the mineral is optically with a small axial angle. 2. Johanngeorgenstadt, Saxony (U. of C.). Canary-yellow coat­ ing. Uniaxial , basal plates. co = 2.01±0.01. e=1.83±0.01.

BISMUTITE. 1. Las Animas, Colo. (U. S. N. M. 9742). Amorphous-looking mass. Indistinctly polarizing. n = 2.25 ±0.03. Birefringence moderate to strong. 2. Cornwall, England (U. of C.). Indefinite material, labeled "bismite." Partly birefracting, with rather strong birefringence. n = 2.2S±0.03. 3. Lone Pine, Inyo County, Calif. (U. of C.). Fibrous to crypto- crystalline after the manner of serpentine. Not entirely homo­ geneous, but the following are the properties of the chief part. Optically , 2E rather large. /3 = 2.17 approximately. Birefringence estimated at 0.05. Properties somewhat variable. 4. Pala, Calif. (W. T. Schaller). Identified by qualitative chemical tests. Nearly colorless, amorphous in appearance. In section it is MEASUREMENTS OF OPTICAL PROPERTIES. 49 made up of matted fibers with Z parallel to the elongation and moderately strong birefringence (estimated at 0.05). j8 is variable but chiefly about 2.15. Optically-f- (?) with a medium to small axial angle. Probably a crystallized or partly crystallized gel. 5. No locality (Cal. Min.). Light-yellowish. Very finely crystal­ line. Birefringence moderate. n = 2.16±0.02, probably a crystallized gel. Bismutite is probably in part amorphous but chiefly a crystallized gel. It is probably not entirely homogeneous nor uniform.

BISMUTOSPH AEEITE. Schneeberg, Saxony (U. S. N. M. 85110). Very thin plates normal to the optic axis. Uniaxial-. w = 2.13±0.01. e = 1.94±0.01.

BOBIERITE. Mexillones, Chile (Col. Roebling). Needles that tend to lie on face (010), which is normal to Y; angle of Z to elongation 29°. Optically 4-, 2E = 125°±5°, 2V = 71°±3° (measured), p

BOLEITE. 1. Boteo, Baja California (U. S. N. M. 80943). Uniaxial-. Blu­ ish green in section and nonpleochroic. w = 2.05 ±0.02. e = 2.03 ±0.02. Not entirely homogeneous, w in part as low as 2.04, in part con­ siderably greater than 2.05. 2. See Percylite (p. 118). BORICKITE. 1. Leoben, Styria (J. H. U. 653). Reddish-brown opaline material. In large part isotropic and reddish brown in section, n ranges from about 1.57 to about 1.67. The darker part has the higher index of refraction, and some fibers show strong birefringence. This material is highly variable and amorphous. 12097° 21 4 50 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

BOUSSINGAULTITE. 1. Artificial boussingaultite. Crystallized from a solution of (NH4)2S04 and MgS04 in molecular proportion by allowing the solu­ tion to stand in a desiccator at 21° C. The supersaturated solution was shaken, and the crystals that formed were studied. Optically +, 2E = 77°±1°, 2V = 50°±1° (measured), p>v (perceptible).. a = 1.469±0.003. 0 = 1.470±0. 003. 7 = 1.479±0. 003. These data agree with the data formerly given. After the satu­ rated solution had stood in a desiccator for two days a second crop of crystals appeared. These crystals were stout tablets, the largest of them a millimeter across and rudely hexagonal in outline with one pair of edges somewhat longer. Extinction is nearly parallel to this longer edge, and Bxa (Z) emerges at an angle of about 35° to the normal to the tablets and in the direction of the long edge. If this face is {110}, the data agree with those formerly given and Y = 6, XAc small. 2. Larderello, Tuscany (Col. Roebling). Optically +, 2V = 55° ± 5° (indices). a = 1.473 ±0.003. 0 = 1.486 ±0. 003. y = 1.539 ±0.003. These data do not agree with the data formerly given, and the material is probably incorrectly labeled. Compare with Bechilite, No. 2 (p. 45). Contains considerable sassolite.

BRACKEBUSCHITE. Cordoba, Argentina (A. M. N. H.). Optically+ , 2V large, pleo- chroism very strong. a L1 = 2.28±0.02; nearly colorless. 0 Li = 2.36 ±0.02; dark, clouded, reddish brown, 7 Lt = 2.48 ±0.02; clear reddish brown.

BRANDISITE. Fassathal (Col. Roebling). Green, chloritic mineral. Optically-, 2V very small, X normal to the cleavage, pleochroic. «= 1.648 ±0.003; pale orange-yellow. 0 =1.660 ±0.003; pale green. 7= 1.660 ±0.003; pale green.

BRANDTITE. Harstig mine, Pajsberg, Sweden (U. S. N. M. 49048). Optically +, 2E = 40°±2°, 2V = 23°±1° (measured), p

BBANNEEITE. Indian Bar, Idaho (type, F. L. Hess). In section isotropic and light reddish brown. nLi = 2.26 ±0.02 (varies a little). 7iNa = 2.30±0.02.

BROCHANTITE. Horn Silver mine, Frisco, Utah (U. S. N. M. 81120). Optically- , 2V=70°±5° (indices), p

BBUGNATELLITE. 1. Italy (Col. Roebling). Plates, uniaxial . « = 1.535. Birefringence rather strong. 2. Mount Ramazzo, Italy (U. S. N. M.). Plates, uniaxial . co =1.540 ±0.003. c= 1.510 ±0.005.

CABRERITE. Laurium, Greece (U. S. N. M. 86105). Optically-, 2V near 90°. X is normal to the cleavage, which is highly perfect. Pale green in section. a= 1.62 ±0.01. j8= 1.654 ±0.003. 7= 1-689 ±0.003. Compare with Annabergite (p. 40).

CACOXENITE. 1. Vogtland, Saxony (U. S. N. M. 3923). Yellowish fibers. Uniaxial+ , slender prismatic crystals, pleochroic. w= 1.580 ±0.003; pale yellow. «= 1.643 ±0.003; canary-yellow. Parts of some of the fibers, especially near the ends, have consider­ ably higher indices of refraction. 2. Trenic, Bohemia (Cal. Min.). Radiating fibers. Uniaxial+ , minute fibers, pleochroic. w = 1.580 ±0.003; pale yellow. e= 1.640 ±0.003; darker yellow. 52 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. 3. Tonopah, Nev. (U. of C.). Uniaxial+, delicate needles, pleo- chroic. co = 1.585±0.003; pale yellowish. e= 1.656 ±0.003; orange-yellow.

CALCIOFEREITE. 1. Battenberg, Bavaria (A. M. N. H.). Pale-yellow powder on quartz. Perceptibly uniaxial , optic axis normal to the plates. io = 1.57 to 1.58 (varies). Birefringence low. 2. Battenberg, Bavaria (Col. Roebling). Uniaxial . w = 1.56. Birefringence very low. In part it appears nearly isotropic and may be partly amorphous. It contains many shreds whose optical properties resemble sericite.

CALEDONITE. Inyo County, Calif. (U. of C.). Optically -, 2V = 85° ± 5° (indices), p < v (barely perceptible). a = 1.818±0.003. j3 = 1.866 ±0.003. 7 = 1.909 ±0.003.

CARACOLITE. Caracoles, Chile (A. M. N. H.). Water-clear, glistening crystals. Optically-, 2V very large, p>v (rather strong). No perceptible cleavage. a = 1.743 ±0.005. /3 = 1.754 ±0.005. 7 = 1.764 ±0.005. Not entirely homogeneous. Some parts show polysynthetic twinning or similar structure with rather large extinction angle; others, after crushing, look like an aggregate of crystals, as if the material were an inversion or alteration product derived from the original crystal. The appearance may be due to complex twinning.

CARNOTITE. Long Park, Montrose County, Colo. (F. L. Hess). Yellow powder. Optically-, 2E = 90°±5°, 2V = 43°±2° (measured), 2V = 40°±5° (indices). Minute tabular crystals normal to X with an angle of 78° ±1° between the edges. Nearly or quite colorless in section. a = 1.750 ±0.005. j8 = 1.925 ±0.005. 7 = 1.950 ±0.005. MEASUREMENTS OF OPTICAL PROPERTIES. 53

CABPHOSIDERITE. Greenland (Col. Roebling). Yellow, botryoidal crusts. Very fine interwoven fibers. Different layers have somewhat different optical properties. Elongation+ , probably optically+. a=1.70±0.03. 7 = 1.SO±0.02. The material is very unsatisfactory. The optical data suggest the possibility that the mineral is jarosite.

CARY1NITE. Langban, Sweden (U. S. N. M. 82744). OpticaUy +, 2E = 78° ± 4°, 2V = 41°±3° variable (measured), p>v (slight). Z nearly normal to cleavage. « = 1.776±0.005. 0 = 1.780 ±0.005. 7 = 1.805 ±0.005. The indices of refraction are somewhat variable (±0.01). The values given are about the average.

CARYOCERITE. Langesund, Norway (Brogger; U. of Stockholm). Isotropic, yel­ lowish brown in section. n = 1.74 ±0.01.

CAKYOPILITE. See Bementite (p. 46). CASTANITE. 1. Chile (A. M. N. H.). Pale, reddish-brown, resinous mass. Opti- cally + , 2E = 53°, 2V = 34°±2° (measured), 2V = 35° (indices), p>v (rather strong); strongly pleochroic. a = 1.527 ±0.003; nearly colorless. /3 = 1.532 ± 0.003; nearly color­ less. 7 = 1.583 ±0.003; rather strong orange-yellow or yellow-brown. 2. Sierra Capra, Chile (Col. Roebling). Hohmannite = castanite. Brown, vitreous crystals. Optically+, 2V rather small, p>v (mod­ erate). No cleavage noticed. a =1.524±0.003; colorless. /3 = 1.530±0.003; nearly colorless. 7 = 1.580 ±0.003; yellow ocher (Ridgway's 17'-*). A partial analysis of this specimen showed 8.6 per cent of MgO. Either the specimens of castanite are incorrectly labeled or castanite is identical with quetenite. See Quetenite (p. 125). 54 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

CELADONITE. Verona, Italy (U. S. N. M. 93080). Very minute fibers with 4- elongation. a = 1.625 ±0.005. 7 = 1.638 ±0.005. Pleochroic as usual. CENOSITE. Nordmark, Sweden (A. M. N. H.). Minute chestnut-brown crystals on chlorite. Optically , 2V = medium large. Brownish and clouded in section and nonpleochroic. a = 1.667 ±0.003. 0 = 1.681 ±0.003. y = 1.683 ±0.003.

CERITE. 1. Riddarhyttan, Sweden (U. of C.). The reddish-brown part of the specimen is made up of an aggregate of a number of minerals,, Mineral A is in slight excess of B, and C and D occur in small amount. A (agrees optically with bastnaesite). Colorless grains, uniaxial+. «= 1.722 ±0.003. e = 1.813 ±0.003. B = Cerite. Nearly colorless grams, pleochroic only in thick sec­ tions. Optically +, 2V = 25° ±3° (measured), p < v (very strong). . a = 1.817 ±0.003; nearly colorless. j3 = 1.817 ±0.003. 7 = 1.821± 0.003; pale reddish. C, optically+, 2V small, p

CERVANTITE. 1. Cornwall, England (U. S. N. M., Shepard collection). Most of the material is perceptibly isotropic, but some is indistinctly birefracting. n =1.88 ±0.02. 2. Kern County, Calif. (U. of C.). Isotropic, with some indis­ tinctly birefracting material. n= 1.98 ±0.01 (about). MEASUREMENTS OF OPTICAL PROPERTIES. 55 3. Kern County, Calif. (U. of C.). Yellow earthy alteration of stibnite. Almost entirely amorphous. n = 1.99 ±0.01. 4. Western Australia (U. of C.). In powder, largely very finely fibrous, with strong birefringence and Z parallel to the fibers. Indices of refraction vary somewhat, probably owing to admixed amorphous material.

5. Fords Creek, New South Wales (U. S. N. M. 82476) . Not homo­ geneous. In part rather strongly birefracting with n>1.98. .In part with n < 1.98. 6. Utah (U. S. N. M. 48208). Indistinctly birefracting. 0 = 2.05 ±0.03. 7. Knoppenberg, Austria (Cal. Min.). Optically-, 2E = 27°±2°, 2V = 15°±1°, dispersion slight. In lath-shaped crystals with X normal to the plates and Z parallel to the elongation. (This speci­ men is probably a carbonate.) a = 1.83 ±0.02. 0 = 2.04±0.02. T = 2.04±0.02. There are also many fibers with faint birefringence and 4- elonga­ tion. n = 2.06 ±0.02. See Stibiconite (p. 136). CHALCANTHITE. Chuquicamata, Chile (U. S. N. M.). Labeled "krohnkite." Optically-, 2E = 92°±3°, 2V = 56°±2° (measured), p

CHALCOLAMPRITE . Narsarsuk, Greenland (Brush Coll. 1671, Yale). Nearly colorless in section and clouded. Isotropic. n averages about 1.87. Varies somewhat.

CHALCOMENITE. Cerro de Cacheuta, Argentina (A. M. N. EL). Associated with azurite. Greenish blue and paler than azurite. In section pale greenish blue and nonpleochroic. Optically , 2ELi = 62°±50, 2Vu = 34° (measured) , p > v (extreme) . The red part of the hyperbolae cross (2V = 0 for blue or green light) . a =1.710 ±0.003. j3= 1.731 ±0.003. 7= 1.732 ±0.003. 56 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

CHALCOPHAN1TE. 1. Ogdensburg, N. J. (U. of C.). Nearly opaque, n extreme, bire­ fringence strong, pleochroism strong. 2. Sterling Hill, N. J. (A. M. N. H.). Uniaxial-, strongly pleochroic, e = deep red, w = nearly opaque. «>2.7. 3. Leadville, Colo. (G. F. Loughlin, U. S. Geological Survey). Fine, fibrous crusts, uniaxial , strongly pleochroic and nearly opaque. Fibers tend to lie on base. Birefringence is extreme. « is some­ what above 2.72. 4. New Discovery dump, Leadville, Colo. (G.F. Loughlin). Coarsely crystalline. Uniaxial , lie on very perfect basal cleavage. Bire­ fringence extreme, strongly pleochroic; e = deep red, w=== nearly opaque. co is much above 2.72. e is near 2.72.

CHALCOSIDERITE. 1. Arizona (U. of C.). Dark-green crystals. In section pale green and nonpleochroic. Optically-, 2ENa = 44°±2°, 2VNa = 23°±l° (measured), 2ELi = 53°±2°, 2VU = 280 ±20 (measured), p>v (very strong), crossed very strong. A section normal to Bxa gives an interference figure which is not black, but when turned so that the hyperbolae are crossed the figure is bordered by blue in one pair of opposite quadrants and red in the other pair. In plane polarized light this section gives no extinction in white light but abnormal red, blue, and green interference colors as the section is turned on the stage of the microscope. Other sec­ tions show sharp extinction in white light. a = 1.773 ±0.003. /3 = 1.840 ±0.003. 7 = 1.845 ±0.003. The optical properties indicate a monoclinic mineral with X = &. 2. Wherl Phoenix, Cornwall, England (U. S. N. M. 47524). Bright- green drusy crystals. Optically-, 2ENa = 44°±3°, 2VNa = 24°±2° (measured), 2ELi=52°±3°, 2VLi = 28°±2° (measured), p>v (very strong), crossed very strong. In thin section nearly colorless, in thicker pieces pleochroic. a =1.775 ±0.003; colorless. . 0 = 1.840±0.003. 7 = 1.844 ±0.003; pale green.

CHENEVIXITE. American Eagle mine, Tintic, Utah (U. S. N. M. 44549). Pale green, opal-like. Very finely crystalline to submicroscopic. Unsat­ isfactory for optical data. n = about 1.88. Birefringence in some of the material rather strong. MEASUREMENTS OF OPTICAL PROPERTIES. 57

CHILDEENITE. 1. Tavistock, England (U. S. N. M. 84674). Optically-, 2V = medium, p>v (strong). a = 1.643 ±0.003. 0=1. 678 ±0.003. 7 = 1-684 ±0.003. 2. Hebron, Maine (U. S. N. M. 82429). Optically - , 2E = 70° ± 5° 2V = 40° ±3° (measured), peosphorite.

CHLOBOM AGNESITE . Artificial MgCl2 made by the ignition of MgCl2 + 6H20. Fibers and plates (001). Uniaxial-. co = 1.675 ±0.005. e = 1.59 ±0.01. Rapidly takes up water. CHLOROPAL. Hungary (U. S. N. M. 51644). Fibrous. a = 1.625±0.01. 7 = 1-655±0.01. Not satisfactory for further data.

CHONDRODITE. 1. Brewster, N. Y. Reddish-brown crystals. Optically + , 2V large. a= 1.625 ±0.005 (varies ±0.01). /3= 1.636 ±0.005 (varies ±0.01). 7 = 1.655 ±0.005 (varies ±0.01). 2. Nya Kopparberg, Sweden. Optically + , 2V large. a= 1.605 ±0.005 (varies ±0.01). /3= 1.618 ±0.005 (varies ±0.01). 7 = 1.635 ±0.005 (varies ±0.01).

CHROMITE. 1. North Carolina. Red-brown in powder.

2. Nottingham, Pa. Contains Cr2O3, 51.21 per cent; Fe (as Fe203) + A12O3, 48.70 per cent. 58 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

CHUHCHITE. Cornwall, England (U. S. N. M. 51447). Perceptibly uniaxial and +. The crystals are rectangular in outline, wedge out on the long edges, and at the short edge have a face normal to the tablets (fig. 7). Z is sensibly normal to the plates. If turned on edge the plates give extinction angles up to 1|° (probably parallel extinction). a = 1.620 ±0.003. 0= 1.620 ±0.003. 7= 1-654 ±0.003. The optical data and habit indicate an orthorhombic mineral with 2V nearly or quite 0. CIMOLITE. 1. Norway, Maine (U. S. N. M. 16177). Kather clear, isotropic grains. 7i=1.564. Considerable admixed quartz occurs in small, well-formed crystals. 2. Bilin, Bohemia. Variety anandite (U. S. N. M. 4076). Not homogeneous; consists in part of amorphous material in which n is about 1.48 and in part of birefracting shreds that have a considerably higher index of refraction. This mineral, in common with the other clay-

ZV'O like minerals, needs further study.

z CLAUDETITE. Schmollnitz, Hungary (Col. Roebling). Opti­ cally +, Y is normal to the plates. a= 1.871 ±0.005. /3 = 1.92 ±0.02. 7 = 2.01±0.01. FIGURK 7. Optical orienta­ tion of tabular crystals of It is difficult to turn the plates on edge. churchite. CLINOCLASITE. Mammoth mine, Tintic, Utah (U. S. N. M. 48108). Optically-, 2V medium, pleochroic. a =1.73 ±0.01; pale blue-green. 0= 1.870 ±0.01; light blue-green. 7 = 1.91 ±0.02; benzol-green.

CLINOHEDRITE. Franklin, N. J. (U. S. N. M. 84365). Optically-, 2V large, Z nor­ mal to cleavage. /3 = 1.670 ±0.003. Birefringence = 0.01. MEASUREMENTS OF OPTICAL PROPERTIES. 59

COBALT CHALCANTHITE. 1. Labeled bieberite. Bieber, Hesse (Col. Roebling). Rose-red coating, pale rose-red in section. Very finely crystalline. Optic­ ally , 2V medium. a = 1.532 ±0.005. (3 = 1.542 ±0.005. 7 = 1.547 ±0.005. This is no doubt a dehydration product of bieberite. 2. Artificial. Pale rose-pink. Optically , 2V medium, dispersion not strong, faintly pleochroic. a = 1.530±0.003; eosine pink (Id).25 0 = 1.548 ±0. 003. 7 = 1.550±0.003; pale rose-pink (71f).25

COEEITLEOLACTITE.

Gen. Trimble's mine, East Whiteland Township, Chester County, Pa. Fibrous crusts. Radiating fibers that have parallel extinction and positive elongation. Nearly or quite uniaxial and optically+ . a; = 1.580 ±0.005. e = 1.588 ±0.005

COLLYRITE. Fichtelgebirge (Col. Roebling). Dull, opaline. Mostly isotropic. n=1.555. This mineral agrees with halloysite that is low in water and has about the composition of kaolinite.

COLUMBITE AND TANTALITE. 1. Canon City, Colo. (U. S. N. M.). Columbite. Specific gravity 5.48. Nearly opaque, faintly pleochroic. j8 = 2.45 (about). Birefringence strong. 2. Dakota (U. of C.). Tantalite. Optically -f, 2V large. Rather strongly pleochroic in red brown, absorption Z>X. a = 2.26 ±0.02. 18 = 2.32 ±0.02. 7 = 2.43 ±0.02. 3. Alabama (U. S. N. M. 8315). Tantalite. Specific gravity 7.30. Optical properties variable. 7 ranges from less than 2.30 to more than 2.40. Strongly pleochroic in red-brown, Z>X.

26 Ridgway, Eobert, Color standards and nomenclature, 1912. 60 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. 4. Amelia, Va. Tantalite (probably manganotantalite). Specific gravity, 6.5. Optically+ , 2V large, ptantalum increases the specific gravity increases, the index of refraction decreases, and the birefringence increases. 5. Ferrocolumbite. Haddon, Conn. (U. S. N. M. 80012). Prob­ ably optically , translucent only on very thin edges. Absorption rather strong, Z>X. 0Li = 2.40 ±0.03. Birefringence extreme. CONICHALCITE. 1. No locality (Cal. Min.). Emerald-green, botryoidal coating. Green, slightly pleochrpic, fibrous crusts. Optically+, 2V very small, Z parallel to elongation. a = 1.765 ±0.005. 0 = 1.77. 7 = 1.790 ±0.005. The indices differ a little in different layers of the crusts. 2. American Eagle mine, Tintic district, Utah. Type, analyzed by Hillebrand (U. S. N. M.). Emerald-green, = reniform coating. In section fibrous, pale green, and slightly pleochroic. Optically+ , nearly or quite uniaxial. No dispersion noticed. Extinction is parallel, and 'Z is along the fibers. w = 1.778±0.003. e = 1.801 ±0.003. The indices differ somewhat in the different crusts.

CONNARITE. "Rottiste," Rottis, Saxony (A. M. N. H.). Sensibly uniaxial , X is normal to cleavage, pleochroism is very faint. The indices of refraction vary 0.02. co = 1.59 ±0.02. Birefringence about 0.03. COOKEITE. Pala, San Diego County, Calif, (analyzed by W. T. Schaller). Hexagonal plates with Bxa normal to the plates. The plates have a uniaxial center and are divided into hexagonal segments. Each segment has the plane of the optic axis parallel to the hexagonal edge. The optical properties are somewhat variable. Optically 4-, 2E ranges from 0 to 90°. 0 = 1.58 ±0.01. MEASUREMENTS OF OPTICAL PROPERTIES. 61

Birefringence about 0.03. The plates have a narrow border with /3 = 1.54 ±0.01. OOPIAPITE. 1. Atacama, Chile (U. S. N. M. 80516). Optically +, 2V = 69° ±5° (indices), p>v (rather strong). X normal to plates, Z parallel to elongation. a = 1.530 ± 0.005; nearly colorless. 0 = 1.550 ±0.005; nearly colorless. 7 = 1.592 ±0.003; yellow. 2. Knoxvillite. Napa County, Calif. (A. M. N. H.). Pale yellow- green powder. Minute tabular crystals that have a rhombic out­ line and an angle of 77$° between the edges. Optically+, 2V = 67°±1° (indices), p>v (strong). X is normal to the plates and Y bisects the acute angle of the rhombs. Plates turned on edge show parallel extinction., Distinctly pleochroic. a = 1.507 ±0.001; colorless. j8 = 1.529 ±0.001; colorless. 7 = 1.576 ± 0.001; yellow green. The mineral is probably orthorhombic. 3. No locality (U. of C.). Labeled "Molybdite." In thin plates resembling those of knoxvillite but with the acute angle truncated and with an angle of about 72° between the sides. 2E = 72°±3°, 2V = 45°±2° (measured). Optically+, 2V = 49°±5° (indices), p>v (strong). X is normal to the plates and Y bisects the acute angle. <* = 1.540±0.003; nearly colorless. 0 = 1.550±0.003; nearly colorless. 7 = 1.600 ±0.003; pale canary-yellow. 4. Leona Heights, Calif, (analyzed by W. T. Sohaller). Six-sided tabular crystals with an angle of 77£° ±1° between the sides. Op­ tically+, 2V = 52°±3° (indices), X emerges from the plates and Z is parallel to the longer edge and bisects the angle (obtuse) of the other two. a = 1.530 ± 0.003; nearly colorless. 0 = 1.541 ±0.003; nearly color­ less. 7 = 1.587 ±0.003; canary-yellow. 5. No locality (W. T. Schaller). Similar to No. 4. Optically+ , 2V moderate, p >v (rather strong). a = 1.525 ±0.005. |8 = 1.543 ±0.003. 7 = 1.590±0.003. 6. Montpelier, Iowa (R. M. Wilke, of Palo Alto, Calif.). Quensted- tite. Pale-sulphur to greenish-yellow crusts. In section very minute fibers and plates. Optically+ , 2V small, X is nearly normal to the plates. a =1.530 ±0.003. <3 = 1.54±0.01. 7 = 1.600 ±0.003. 62 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

7. Blythe, Calif. Optically +. 2V moderate, p > v (strong). X nearly normal to the cleavage: Section normal to X shows inclined extinction. a =1.510 ±0.005, colorless. j3 = 1.535 ±0.003, colorless. 7 = 1.575 ±0.003, yellow. The available optical data on oopiapite and some related iron sulphates are assembled in the accompanying table for comparison. Optically sideronatrite is very much like some copiapite, except for its fibrous structure. Castanite and quetenite are very much alike and are probably identical, provided the specimens examined are correctly labeled, and there seems no reason to suspect that they are not. They differ sufficiently from copiapite to make it seem probable that they represent a distinct species. The other ten specimens, in­ cluding ihleite, janosite, copiapite, quenstedtite, and knoxvillite, probably represent a single mineral, copiapite. They occur in similar tabular crystals, and all show the same optical orientation and similar pleoohroism. However, they differ considerably in their indices of refraction and must differ somewhat in their chemical composition. TABLE 3. Optical properties of copiapite and some related minerals.

Optical 2V Optical Name and locality. Habit. at 0 7 char­ and dis­ acter. persion. orientation.

1.508 1.525 1.586 + 56° Gordo, Chile. p>u Z // fibers. Knoxvillite. N a p a Rhombic 1.508 1.528 1.576 + 66° X=c. County, Calif. plates, <77£° P>" Y bisects acute angle. Copiapite.o Copiapo..... Orthorhombic. 1.506 1.529 1.573 + 73° 31' X near c. Z=o. Ihleite,o Vignerea, Elba. Rhombic or 1.507 1.531 1.575 + . 74° 43' X=c. six-sided Z bisects acute plates, (001) angle. 78°. 72° 55' .....do...... 1.509 1.532 1.577 + Do. Elba. Castanite, Chile...... Massive...... 1.527 1.532 1.583 + 34° p>!> 1.510 1.535 1.575 + Moderate p>u strong. 1.530 1.535 1.582 + 32° X or Y. Chile. p>V i cleavage. Quenstedtite,* Mont- Fibers, plates. 1.530 1.54 1.600 + Small. X j_ plates. pelier. Copiapite, L e o n a Six-sided tab­ 1.530 1.541 1.587 + 52° X j_ plates. Heights, Calif. lets, <77$°. Z // long edge. Copiapite (?)...... Six-sided tab­ 1.525 1.543 1.590 + Rather X=c. lets, (001). small. Z // long edge. Tablets, (001) 1.520 1.547 1.572 Near 90° 72°. Copiapite, Atacama, Plates. {101> 1.530 1.550 1.592 + 69° X=c. Chile. <00l}. Z // elongation. Copiapite, California.. . . Six-sided tab­ 1.540 1.550 1.600 + 45° X=c. lets, <72°. p>U Z // short edge.

a Manasse, Ernesto, Identita fra lo considetta ihleite elbana e lo copiapite: Soc. toscana sci. nat. Proc. verb., vol. 20, pp. 1-14, Pisa, 1911. 6 Trie original quenstedtite from Chile was optically negative. e Weinschenk, E.. Ueber den Janosit und seine Identitat mit Copiapit: Foldtani Kozlony, vol. 36, pp. 224-228,1906. MEASUREMENTS OF OPTICAL PROPERTIES. 63

CORKITE. Beaver County, Utah (W. T. Sohaller). Biaxial, optically . 0=1.930 ±0.01. Birefringence weak. The plates show abnormal green interference colors. CORNWALLITE. Cornwall, England (Col. Roebling). Green spherulites. Under the microscope the material is seen to be made up of very fine inter­ woven fibers in spherulites, with concentric layers having somewhat variable optical properties. The optical properties are not entirely satisfactory. The following data are believed to be correct but may be partly in error. Optically+ with a small optic angle. Most of the fibers show negative elongation but some show positive elongation. a = 1.81 approximately. 0 = 1.815 ±0.003 in considerable part. 7 = 1.85 approximately.

CORUNDOPHILITE. Chester, Mass. (U. S. N. M. 18180). Deep-green plates. Opti­ cally+, 2E variable but averages about 50°, 2V = 31° approxi­ mately, p

CROCIDOLITE. Locality unknown (U. of C.). Very minute fibers. Optically -f, 2V moderate (?). 0 = 1.70±0.01. Birefringence rather low. CROCOITE. Beresowsk, Urals (U. of C.). Optically+ , 2V = 57° ±( indices), p>v (very strong). «Li =2.29.±0.02. 0ti = 2.36 ±0.02. 7lil = 2.66 ±0.02.

CRONSTEDTITE. Kuttenberg, Bohemia (U. S. N. M. 52035). Strongly pleochroic, nearly opaque to dark reddish brown, translucent only in thinnest splinters. w=1.80±0.01. 64 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

OROSSITE. 1. North of Berkeley, Calif. (U. S. Geol. Survey). Optically-, 2V rather large, pv (very strong), Z = &, gives no extinction in white light owing to strong dispersion, Y^Ac about 10°. Pleochroic. a = 1.657 ±0.003; pale yellowish, nearly colorless. /3 = 1.659± 0.003; deep blue. 7 = 1 -663 ±0.003; deep violet.

CUPRODESOLOIZITE. 1.Arizona. (Type analyzed by R. C. Wells.) Fibers with nega- \ tive elongation and strong pleochroism. Optically , 2V = 73° i about (indices). p>v (strong). I a=2.17±0.02; nearly colorless. /3 = 2.26±0.02; reddish brown. 7 = 2.32 ± 0.02; reddish brown. 2. Oruro, Bolivia. Dark olive-green grains. The powder is canary-yellow. Optically-, 2E = 120°±10°, 2V = 47°±5° (meas­ ured). p>u (strong). In transmitted light the material is canary- yellow and weakly pleochroic. j

au = 2.21 ±0.01. /3Li = 2.31 ±0.01. TLI =2.33 ±0.01. *

CUPROTUNGSTITE. '! Cave Creek, Ariz. (analyzed by W. T. Schaller). Green in section ! and very finely crystalline. . / n = 2.15±0.02. Birefringence strong. CUSPIDINE. Vesuvius, Italy (U. S. N. M. 85206). Optically+ . a = 1.590 ±0.003. j8= 1.595 ±0.003. 7 =1.602 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 65

CYANOTKICmTE. 1. Tintic district, Utah (A. M. N. H.). Wool-like aggregates of minute blue fibers. Optically + , 2 V = 83 ° ± 5° (indices) . Z is parallel to the length, X emerges from the flat face, pleochroic. a =1.588 ±0.003; nearly colorless. 0 = 1.61 7 ±0.003; pale blue. 7 = 1 .655 ± 0.003 ; bright blue. 2. Tintic district, Utah (F. M. N. H., Chicago). 0 = 1.616; otherwise similar to No. 1. 3. Chile (U. of C.). Long, flat, greenish-blue laths and fibers. Optically , nearly uniaxial, 2E = about 10°, 2V = 6° ±2°, dispersion not perceptible. X is normal to the laths and Z parallel to the elongation. It is very difficult to turn the laths on any but the flat face. a = 1.720 ±0.003. 0 and 7 = 1.724 ±0.003. This is probably not cyanotrichite. Its optical properties do not correspond with those of any known species. CYPRUSITE. 1. Cyprus (Col. Roebling). Very finely crystalline, in part fibrous, in part nearly isotropic and probably a metacolloid. In section canary-yellow. Optically , 2V = medium large. about. Birefringence low. The specific gravity given for cyprusite (1.7 to 1.8) is exceptionally low for a mineral of its composition, as is also the index of refraction of this specimen. 2. Cyprus (Prof. Lacroix). Minute crystals, hexagonal outline. Probably rhombs with prominent base. 'Sensibly uniaxial, op­ tically . co = 1.830 ±0.005. « = 1.72±0.01. This is probably jarosite and agrees more nearly with the original description of cyprusite than does specimen No. 1.

DANALITE. Rockport, Mass. (U. S. N. M. 45943). Colorless, clouded, isotropic. n = 1.737±0.003. 12097° 21 5 66 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

DAPHNITE. Camborne, Cornwall, England (Col. Roebling). Dark-green chlo- ritic mineral in fine aggregates of fibers and basal plates. Optically , 2V near 0, pleochroic. a =1.643±0.003; yellowish, nearly colorless. /? = 1.649±0.003; gseen. 7 = 1.649 ±0.003; olive-green.

DARAPSKITE. Santa Catalina, Chile (Col. Roebling). Glassy crystals. Opti­ cally-, 2E = 40°±2°, 2V = 27°±1° (measured), 2V = 26° (indices), p>v (rather strong). Perfect cleavage sensibly normal to X and this section shows polysynthetic twinning similar to that of plagio- clase, with the composition plane sensibly normal to the cleavage. Extinction on this section against the lamellae is symmetrical and the angle of Z to the lamellae = 12°. There is another perfect cleav­ age or parting parallel to the composition plane of the twinning. a = 1.391 ±0.005. 0=1.481 ±0.003. 7= 1.486 ±0.003. The mineral is probably monoclinic, with X = 6, ZAc = 12°, com­ position plane {100}, perfect cleavages {100} and {010}.

DAUBREEITE. Cerro de Taza, Bolivia (Col. Roebling). Yellow, earthy powder. Very finely crystalline. 0 = 1.91 ±0.01. Birefringence about 0.01. DAVIES1TE. Mina Beatriz, Sierra Gorda, Mexico (Col. Roebling). Clear crystals and fibers. Optically +, 2V nearly 90°, p < v (rather strong). May be optically , 2V nearly 90°, p>v (rather strong). The axial angle is so near to 90° that the optical character is uncertain. a =1.744 ±0.003. |8 = 1.752 ±0.003. 7 = 1.760 ±0.003. DAWSONITE(?) Siena, Italy (U. S. N. M. 46463). Cotton-like aggregates of minute fibers. The elongation is + and extinction is parallel. Probably optically+ , absorption is rather strong. a =1.505 ±0.003; gray and clouded. 0 = 1.515 ±0.005; gray and clouded. 7 = 1.535 ±0.005; clear and colorless. MEASUREMENTS OF OPTICAL PROPERTIES. 67

This is entirely different from the original dawsonite from Montreal, as described by Graham.28

DERBTLITE. - Mina Geraes, Brazil (A. M. N. H.). Minute crystals. Uniaxial + , or a very small axial angle. o>L1 = 2.45 ±0.02. L1 = 2.51 ±0.02. e DESCLOIZITE. Mammoth mine, Arizona (U. of C.). Orange-red crystals; 2V nearly 90°, optically , p

a = 2.185±0.01. /3 = 2.265±0.01. 7 = 2.35±0.01.

DESTINEZITE. Vis6, Belgium (Prof. Lacroix). Nearly colorless, earthy. Under the microscope it is seen to be made up of minute tabular crystals with a hexagonal outline. Optically +, 2V small, p > v (rather strong). X is nearly normal to the tabular face and Z' makes an angle of about . 16° to the long edge. When 'turned on the face forming the long ! edge the crystals show the emergence of Y and give an extinction Z'

DIABANTITE. 1. Bergen Hill, N. J. (U. S. N. M. 13562). Very minute shreds "tangled together.'' Optically , 2V small (?), dark olive-buff in section and faintly pleochroic. /3 = 1.605 ±0.005. Birefringence rather strong. 2. Wilson's quarry, Plainfield, N. J. (E. T. Wherry). Optically- , 2V = rather large, Z is parallel to the elongation of the fibers which tend to lie on a face normal to X. Pleochroic in gray-green, with absorption Z > Y > X. a=1.54±0.01. |8 = 1.59±0.01. y = 1.605 ±0.005. Measurements of the indices differ slightly.

DIADOCHITE. 1. Kremnitz, Hungary (Col. Roebling). Brown, opaline. Per­ ceptibly isotropic, clear yellow, and homogeneous.

2« Graham, R. P. D , Roy. Soc. Canada Trails., vol. 2, section 4, p. 165, 1908. 68 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

2. Frelingyiote, Styria, Austria (U. S. N. M. 48450). Crypto- crystalline. Birefringence is moderate to rather strong.

Probably not diadochite.

DICKINSONITE. Branchville, Conn. (U. S. N. M.). Optically + , 2V moderate, p>u (rather strong), Y is nearly normal to the plates, X = &, pleochroic. a = 1.658 ± 0.003 ; pale olive-green. /3 = 1.662 ± 0.003 ; paler olive- green. 7 = 1.671 ± 0.003 ; very pale yellowish green.

DIETRICHITE. Felsobanya, Hungary (A. M. N. H.). White fibers. Optically + (it may possibly be ), 2V large, fibers turned so that X is normal to them show the angle Z to elongation 29° ± . Fibers nearly normal to Y show perceptibly parallel extinction. The mineral is therefore probably monoclinic, with X = & and Z A c = 29° ± . a= 1.475 ±0.003. /3 = 1.480 ±0.003. 7 = 1.488 ±0.003.

DIETZEITE. Atacama, Chile (A. M. N. H.). Sulphur-yellow glassy crystals. Optically , 2V large, p

DIHYDRITE. 1. Dihydrite, Bogolo, Portugal (Col. Roebling). Dark-green crystals. 2V about 90°, in part optically , p>v (stiong), in part optically + , pZ. a = 1.719 ±0.003. |8 = 1.763 ±0.003. 7 = 1.805 ±0.003. 2. Pseudomalachite, Hungary (U. of C.). Green, malachite-like crusts. Very finely fibrous, Z nearly parallel to the fibers. a=1.73±0.01. . 7 = 1-807 ±0.005. MEASUREMENTS OF OPTICAL PROPERTIES. 69

DOUGLASITE. Douglashall, Westerregeln, Germany (Col. Roebling). Perceptibly uniaxial, optically + ; the crystals tend to lie on the base. co-1.488 ±0.003. =1.500 ±0.003.

DUFEENITE. 1. Saxony (U. of C.). Crystals with zonal growths showing varia­ ble optical properties, especially the axial angle. All show Z normal to the cleavage. Cleavage pieces show no extinction in white light but abnormal green, orange, and red interference colors over a wide angle. Fibers turned normal to the plane of Y and Z show sharp, parallel extinction in white light. A. The greater part of the material is optically +, 2V medium to 90°, p>v (marked), crossed extreme, pleochroism intense, absorp­ tion Z>X>Y. a= 1.830 ±0.005; bright green (when 2V is small, brownish). (3 = 1.840 ±0.005; very pale yellowish to nearly colorless. 7 = 1.885 ± 0.005; dark reddish brown. B. 2V may pass through 90° and some of the crystals may be optically , with large 2V and p Y >X. a = 1.840 ± 0.005; pale yellowish. 0= 1.845 ±0.005; rather dark reddish brown, becoming bright green as 2V becomes small. y = l -89 ± 0.01; dark reddish brown to dark green. 70 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

One piece showed 2V small, p v. These data show that for dufrenite 2V appears to decrease from large in type C, with pv to 90°, and to become optically with p < v and to decrease. The value of 7 remains from 1.885 to 1.890; the value of the ray that vibrates parallel to the cleavage and normal to the fibers remains practically constant at 1.840, but the value of the ray that vibrates in the direc­ tion of elongation varies greatly. It is /3 in type C and has a value of 1.845 ± , but it is a in type A and has a value of 1.830 ± .

DUFRENOYSITE. Binnenthal, Switzerland (U. S. N. M. 84125). Dark red-brown in section and nearly opaque. Properties not entirely satisfactory.

Birefringence very strong.

DUMORTIERITE. California (U. S. N. M. 85068). Optically- , 2V small, pleochroic but pale in color, X parallel to length. a = 1.670 ±0.003; pale blue-violet. 0 =-- 1 .691 ± 0.003 ; nearly colorless. 7 = 1 .692 ± 0.003 ; nearly colorless.

DURANGITE. Durango, Mexico (U. S. N. M. 81712). Optically-, 2V = 57°± (indices), dispersion not perceptible, pleochroic.

a = 1.634 ±0.003; orange-yellow. 0 = 1.673 ±0.003; pale orange-yellow. 7 = 1.685 ±0.003 ; nearly colorless.

DURDENITE. 1. Honduras (U. of C.). Pale greenish-yellow pyramidal, prisms. Optically-, 2ENa = 44°±2 0, 2VNa = 22°±l° (measured), 2V = 21°± (indices), p>v (very strong). X _|_ a face or more likely a perfect cleavage. Two other perfect cleavages (possibly crystal faces) occur normal to this one and with an angle of about 72° between them. Y bisects the acute angle between these cleavages. Pleochroism is strong and absorption Z>Y>X.

a = 1.702 ±0.005 ; nearly colorless. j8 = 1.955 ±0.005; pale yellow with a greenish tinge. 7 = 1.965 ±0.005 ; rather pale sulphur-yellow. MEASUREMENTS OF OPTICAL PROPERTIES. 71

The mineral appears to be orthorhombic. 2. Calaveras County, Calif. (U. of C.). Labeled "Tellurium." Pale greenish-yellow spherulites coating fracture surfaces on a telluride ore. Optically-, 2E = 48°±3°, 2VNa = 24 0 ±2 0 (measured), p>v (very strong), tend to lie on a cleavage normal to X. a=1.710±0.005. 0 = 1.94 ±0.01. 7 = 1.95±0.01. The optical properties are identical with those of durdenite, for which mineral California is a new locality.

DYSANALYTE. Magnet Cove, Ark. (U. S. N. M. 51431). Cube. Isotropic, clouded and dark brown, nearly opaque in section. 71 = 2.33 ±0.02.

ECDEMITE. Langban, Sweden (U. S. N. M.). Yellow-green coating of very fine crystals. Uniaxial , cleavage {001}. o>Li = 2.32 ±0.02. eLi = 2.25 ±0.02.

EGLESTONITE. Terlin'gua, Tex. (U. S. N. M. type material). Probably isotropic with anomalous birefringence. nu = 2.49 ±0.02.

EMMONSITE. Cripple Creek, Colo. (U. S. N. M. 86846). Optically-, 2V small, p>v (strong), fibers and plates, colorless in section.

a=1.95±0.02. 7 = 2.10±0.02.

ENDLICHITE. Hillsboro, N. Mex. (U. S. N. M. type). Hexagonal prisms. Uni­ axial . w = 2.25±0.01. e = 2.20±0.01.

ENIGMATITE. Naujakasik, Greenland (Princeton No. 3431). a = 1.80 ±0.01. Birefringence rather low. Pleochroism very strong. X = pale reddish brown, Z = nearly opaque. 72 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

EbSPHORITE. 1. Branchville, Conn. (U. S. N. M.). Optically-, 2V medium, PChildrenite" (U. S. N. M. 82429). Optically-, 2E = 70°±5°, 2V = 40°±3° (measured), P

ERINITE. Mammoth mine, Tintic, Utah (U. S. N. M. 48112). Small green fibers. Z is j_ perfect cleavage, Y// elongation. Optically , 2V moderate, pERIONITE. Durkee, Oreg. (U. S. Geol. Survey). Wool-like fibers. Optically+ . a = 1.438 ±0.003. 7 = 1.452 ±0.003.

ERYTHRITE. Schneeberg, Saxony (U. S. N. M. 82265). Optically + , 2V very large, X normal to the plates, angle of Z to elongation 30°+ 1°, pleochroic, absorption Z > Y and X. a = 1.629 ±0.003; pale pinkish. 0 = 1.663 ±0.003; pale violet. 7 = 1.701 ±0.003; red.

ESCHYNITE. 1. Ilmen Mountains, Siberia (U. S. N. M. 78415). Black in mass. In powder, conchoidal grains, reddish brown and perceptibly isotropic. n = 2.26±0.01. MEASUREMENTS OF OPTICAL PEOPERTIES. 73

2. Hittero, Norway (U. S. N. M.). Reddish brown in powder and sensibly isotropic. ?i = 2.205±0.01.

ETTRINGITE. Ettringer, Prussia (U. S. N. M. 85109). Very minute fibers with negative elongation. Very unsatisfactory. n=1.49±0.01. Birefringence 0.01 ±. EUCHROITE. 1. Libethen, Hungary (U. S. N. M.). Emerald-green crystals. Optically + , 2E = 51°±1°, 2V = 29°±1° (measured), p>v (mod­ erate) . a = 1.695±0.003. /3 = 1.698±0.003. 7 = 1.733 ±0.003. Bright bluish green in section and faintly pleochroic or non- pleochroic. 2. Utah (U. of C.). Optically+ , 2V = 62°±5° (indices), pEUCRYPTITE. Branchville, Coiin. (U. S. N. M. 82522). Probably uniaxial-. co = 1.54 ±0.01. Birefringence rather low. Not very satisfactory.

EULYTITE. Schneeberg, Saxony (U. S. N. M. 85192). . n = 2.05±0.01. Birefringence very low. EUXENITE. Hittero, Norway (U. S. N. M. 4.9001). In section reddish brown and perceptibly isotropic. 74 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

FAIRFIELDITE. Branchville., Conn. (W. T. Schaller). Optically +, 2V very large, p > v (moderate). a =1.636 ±0.003. 0 = 1.644 ±0.003. 7 = 1.654±0.003.

FARATSIHITE. Faratsihi, Madagascar (Prof. Lacroix). Pale-yellow compact mass. Under the microscope it is seen to be made up of minute fibers that have + elongation. Optic properties vary a little. 0 = 1.560 ±0.01. Birefringence about 0.02. Part of the material is submicroscopic in crystallization and has a somewhat lower index of refraction.

FELSOEBANYITE. Felsobanya, Hungary (Col. Roebling). Broad, rectangular laths. Optically + , 2E = 77°±3°, 2V = 48°±2° (measured), P >v (percep­ tible). Z is normal to the flat face and X is parallel to the elonga­ tion. a = 1.516 ±0.003. 0 = 1.518±0.003. 7 = 1.533 ±0.005.

FERBERITE. See Wolframite (p.157).

FERGUSONITE. Baringer Hill, Tex. (F. L. Hess). Brown in section and percepti­ bly isotropic. n = 2.19 ±0.02.

FERNANDINJTE. ' Type, Minasragra, Peru (W. T. Schaller). An aggregate of very minute, strongly birefracting fibers. Nearly opaque, and data are very unsatisfactory. n = about 2.05.

FERRITUNGSTITE. Germania mine, Deer Trail district, Wash. (U. S. N. M. 86985, type material). Yellow powder. Minute fibers show + elongation. Probably uniaxial . co = 1.80. e=1.72. MEASUREMENTS OF OPTICAL PROPERTIES. 75

FERROCOLUMBITE. See Columbite (p. 60). FIBROFERRITE. 1. Cimarron, Colo. (F. L. Hess). Fibers have Z parallel to the elongation, feebly pleochroic. a. = 1.525 ±0.003; nearly colorless. 7 = 1.565 ±0.003; pale yellow. Probably optically + with small axial angle. 2. Genette Mountain, Ariz. (U. of C.). Nearly or quite uniaxial and optically+ . Fibers have positive elongation. Faintly pleo-

FILLOWITE. Branchville, Conn. (W. T. Schaller). Optically+ , 2V moderate, ,p

FISCHERITE. Two specimens labeled "Fischerite" were examined, but probably neither is fischerite. 1. Eoman-Gladna, Hungary (A. M. N. H.). Perceptibly isotropic, colloidal crusts that have somewhat variable indices of refraction. n= 1.51 ±0.02. Compare with Planerite (p. 173) and Evansite (p. 172). 2. Roman-Gladna, Hungary (Yale). White enamel, opal-like. / In section the mineral is made up of layers of minute fibers that show + elongation and nearly or quite parallel extinction. Different layers differ somewhat. n=1.47±0.01. Birefringence moderate. See Vashegyite (p. 279). FLINKITE. Harstig mine, Pajsberg, Sweden (Col. Roebling). Minute dark- greenish prismatic crystals. In section not deeply colored and not strongly pleochroic. Optically + , 2V large, p>v (perceptible). «= 1.783±0.003; pale brownish green. 0= 1.801 ±0.003; yellowish green. 7 = 1.834 ± 0.003; orange-brown. 76 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

FLORENCITE. Minas Geraes, Brazil (Col. Roebling). Light-brown crystal grains, Uniaxial +. o)= 1.680 ±0.01. Birefringence about 0.005.

FLUELL1TE. Stenna Gwyn, Cornwall, England (A. M. N. H.). Clear crystals coating quartz. Optically+ , 2V = 85°± (indices), p

FLUOCERITE. Osterby, Sweden (Yale, B. ("oil. 4424). Optically + , uniaxial. 0=1.615±0.003.

Birefringence about 0.002. The mineral is filled with inclusions which have a strong birefringence.

FORSTERITE. Nepheline basalt from Idaho. Analyses of the rock indicate a nearly pure magnesian olivine. Optically+ , 2V = 90°±5° (indices), dispersion slight. a= 1.640 ±0.003. |8=F 1.660 ±0.003.. 7= 1-680 ±0.003.

FRANKLINITE. Franklin Furnace, N. J. (U. of C.). Isotropic. Reddish brown in section. nLi = 2.36 ±0.02.

FREMONTITE. 1. Near Canon City, Colo. (type material from W. T. Schaller). Optically +, 2V very large. Polysynthetic twinning, with symmetri­ cal extinction on cleavage piece, angle of Z to lamellae = 29°. ce=1.594±0.003. /3= 1.603 ±0.003. 7= 1.615±O.C03. 2. Austria (W. T. Schaller). 2V nearly 90° and optical character uncertain. 7=1.618±0.003. Birefringence rather strong. MEASUREMENTS OF OPTICAL PROPERTIES. 77

FRIEDELITE. 1. Taylor mine, Franklin Furnace, N. J. (Col. Roebling). Opti­ cally , 2V small. /3=1.65 ±.0.01. Birefringence about 0.03. 2. Pajsberg, Sweden (A. M. N. EL). Rose-red tabular crystals. Uniaxial , e normal to perfect cleavage. Nearly colorless in section. co =1.664 ±0.003. =1.629 ±0.003.

FUCHSITE. Washington, Ga. (U. S. N. M. 18886). Variety pagodite. Opti­ cally , 2V moderate, p > v (rather strong), nearly colorless in section. |8= 1.595 ±0.003, Birefringence as in Muscovite (p. 252).

G-ADOLINITE. 1. Hackberry, Ariz. (F. L. Hess). Pale green in section and non- pleochroic. Specific gravity, 4.32. Optically +, 2V moderately large. a= 1.780 ±0.003. 7= 1.785 ±0.003. 2. Baringer Hill, Tex. (F. L. Hess). Pale green in section and isotropic. Specific gravity, 4.3. n= 1.780 ±0.003. 3. Devils Head mine, Douglas County, Colo. (analyzed, Eakins) (U. S. N. M.). In section pale greenish. Isotropic. Specific grav­ ity, 4.6. n= 1.783 ±0.003. 4. Kararfvet, Sweden (U. S. G. S.). Pale green in section and nonpleochroic. Optically -f, 2V moderate, p < v (rather strong). Spe­ cific gravity, 4.0. a= 1.772 ±0.003. 7 = 1-777 ±0.003. 5. Hooking Hollow, Tex. (F. L. Hess). Dark olive-buff in sec­ tion. Isotropic. Specific gravity, 3.6. n = 1.710±0.003. This is probably not gadolinite. Compare with Rowlandite (p. 129). 6. Baringer Hill, Tex. (F. L. Hess). Dark olive-buff in section. Isotropic. n= 1.710 ±0.003. Almost identical with specimen No. 5. 78 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

GAGEITE. Franklin Furnace, N. J. (Col. Roebling). Minute, colorless needles; or laths. Optically , 2V moderate, p

GANOMALITE. Jacobsberg, Sweden (N. M. N. H., Stockholm). Pale yellowish,, waxy grains. Uniaxial +.

co = 1.910 ±0.005. e=1.945±0.005.

GEARKSUTITE. Ivigtut, Greenland (A. M. N. H.). White, chalky. Optically-,, 2V moderate. Minute fibers or prisms. X is normal to the fibers,. Y makes a large angle with the fibers. The mineral is probably monocljnic, with X = & and the angle of Y to the elongation large. a = 1.448 ±0.003. j8 = 1.454 ±0.003. 7 = 1.456 ±0.003.

GEIKIELITE. Ceylon (Col. Roebling). Uniaxial . In section rather faintly pleochroic in red-brown, with absorption e >co. co = 2.31±0.02. e = 1.95±0.01.

GIBBSITE. 1. Dundas, Tasmania (U. S. N. M. 84868). White, fluffy coating.. Imperfect plates and fibers, which show a highly perfect cleavage; and Z emerging from the plates. Optically+, 2V very small. a and |8 = 1.565 ±0.010. Birefringence 0.03 ±. 2. District of Kussihsk, Urals (U. S. N. M.). Similar to No. 1. a and j8 = 1.565±0.003. 7 = 1.58±0.01. 3. Zlatoust, Siberia (U. S. N. M.). Similar to No. 1. a and 0 = 1.572 ±0.005. Birefringence moderate. 4. Richmond, Mass. (U. S. N. M.). White enamel-like stalactites.. Rather coarse fibers, with a perfect cleavage along the fibers. Z is. MEASUREMENTS OF OPTICAL PROPERTIES. 79

inclined at a considerable angle to the normal to the fibers. Opti­ cally + , 2V very small. Some zonal growths. a and 0 = 1.567 ±0.003. 7 = 1.589 ±0.003. 5. Chester, Mass. (U. S. N. M.). Similar to No. 4. Optically + , 2V ranges from rather small to 0. Zonal banding has somewhat different optical properties. a and 0 = 1.566 ±0.003. 7 = 1.585 ±0.003.

GILPINITE. 1. Gilpin County, Colo. (U. S. N. M.). Labeled "Uranopilite." Minute greenish-yellow lath-shaped crystals. Optically , 2V near 90°, p > v (very strong); in small part optically +, p < v (very strong). Laths normal to X show polysynthetic twinning with composition plane normal to the flat face and parallel to the elongation. These laths show symmetrical extinction with the angle of Y to the lamellae 5$°. Faintly pleochroic. a = 1.577 ±0.003; colorless. 0 = 1.596 ±0.003; nearly colorless. 7 = 1.616±0.003; pale yellowish. 2. Colorado (A. M. N. H.). Labeled "Uranopilite/' Minute, greenish-yellow, lath-shaped crystals. . Optically , 2V = 86°±3° (indices). X is normal to the laths; YA elongation, 8°; dispersion of bisectrices rather strong. Faintly pleochroic. « = 1.575 ±0.003; colorless. j8 = 1.594 ±0.003. 7 = 1.611 ±0.003; canary-yellow. 3. Central City, Colo. (Cal. Min.). Labeled "Johannite." Minute greenish-yellow lath-shaped crystals. Optically +, 2V near 90°. pgypsum mixed with them. The laths show polysynthetic twinning, and the composition plane is normal to the flat face and parallel to the length. The extinction is symmetrical and YA elongation = 5°. X is sensibly normal to the laths. Some crystals, 80 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. probably turned on end, are rhombic in outline with Z parallel to one edge. Optically +, 2V large, p < v (strong). a = 1 .575 ± 0.003; nearly colorless. 0 = 1.592 ± 0.003; pale yellow. 7 = 1.612 ± 0.003; canary-yellow. Evidently the four specimens are identical. The mineral is monoclinic and occurs in lath-shaped crystals (010), elongated along c. Lamellar twinning (100). X=-6, Y /\c = 5%° to 8°.

GLOCKERITE. Zuchmantel, Silesia (U. of C.). Limonite-like porous crusts. In sec­ tion clear, red fibers, very minute and intertwined. Optical character not determined. « = 1.76±. 7 = 1.81±. The properties are somewhat variable, but the average values for the indices of refraction are as stated above.

GOETHITE. 1. No locality (U. of C.). "Limonite." Optically , 2V moderate, p>v (very strong). Elongation of fibers is +. a = 2.18±0.01. 0 = 2.28±0.01. 7 = 2.31 ±0.01. 2. Antwerp, N. Y. (LT. of C.). "Limonite." Radiating fibers. Optically , 2V moderate, p >v (very strong). Y normal to cleavage and Z parallel to elongation. Absorption rather strong in yellow, Y>Z>X. a = 2.19±0.01. 0 = 2.31 ±0.01. 7 = 2.33 ±0.01. 3. Ishpeming, Mich. (U. S. N. M. 44775). Labeled "Xantho- siderite." Pale-yellowish woody fibers. Optically , 2V large, p > v (very strong). The fibers tend to lie on a face normal to Y, Z parallel to elongation. Faintly pleochroic in reddish brown. Absorption YandZ>X. a = 2.15±0.01. 7 = 2.27±0.01. 4. Colorado (U. of C.). Optically , nearly uniaxial, 2V small but variable, pY>X. Translucent and not very deeply colored in section. «Li = 2.21±0.01. 0Li and 7u= 2.35 ±0.01. 5. Thuringia (Harvard). Labeled "Xanthosiderite." Optically , 2V small, p>v (extreme), X is normal to the perfect cleavage; Z MEASUREMENTS OF OPTICAL PROPERTIES. 81 is parallel to the fibers. Moderately pleochroic with absorption X

GONNARDITE. Chaux de Bergonne, Puy-de-D6me, France (W. T. Schaller). Optically -f-, 2E = 83°±10°, .2V = 52°±6° (measured). Y is parallel to the fibers, which tend to lie on a face normal to X. a = 1.514 ±0.005. 0= 1.515 ±0.005. 7 = 1.520±0.005. The properties are somewhat variable.

GOSLARITE,

1. Goslar, Harz Mountains, Germany (U. S. N. M.). The sample is in a sealed tube, but the mineral is partly altered to a white powder. A. The fresh center is vitreous and has the following optical properties. 2V very near 0. a = 1.450±0.003. 0 and 7 = 1.481 ±0.003. B. The white alteration product is very finely crystalline and has a moderate birefringence and a mean index of refraction of 1.570±0.005. 2. Gagnon mine, Butte, Mont. (U. S. N. M. 83637). Although the material has been kept in a sealed tube, it has completely altered to an aggregate of minute fibers that have elongation, moderate birefringence, and a mean index of refraction of 1.600 ±0.01.

GRAFTONITE. Near Grafton, N. H. (U. S. N. M. 85012). Optically+ , 2V small, p>v (rather strong), clear and colorless in section. a =1.700 ±0.003. j8= 1.705 ±0.003. 7 = 1.724 ±0.003.

GRIPHITE. 1. Float near Keystone, S. Dak. (F. L. Hess). Qualitative tests show it to be a hydrous phosphate of manganese. Brownish to yellowish in section and isotropic. w=1.63 to 1.65. A little birefracting. material. 2. Unknown locality in South Dakota (F. L. Hess). Similar to No. 1. Isotropic. w = 1.65 variable. 12097° 21 6 82 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

GUARINITE. Monte Somma, Vesuvius (U. S. N. M. 47065). A. "Guarinite." Pale-yellow tabular crystals hi cavities. Colorless hi section. Thick pieces are pleochroic hi yellow. Optically , 2V rather large, p

HAIDINGERITE. Joachimsthal, Bohemia (R. M. Wilke, Palo Alto, Gain0.). Minute aggregates of soft, glassy crystals. Optically + , 2E = 102°±5°, 2V = 58°±3° (measured), 2V = 60° (indices) . Dispersion slight. In outline cleav­ age pieces are commonly acute rhombs with an angle of about 33° between the edges (fie. 8). X is normal FIGURE 8.-Optical , . , , v ,.° ° orientation of to this cleavage and i bisects the acute angle of common cleavage ^e rhombs. There is another cleavage (or crystal fragments <010> , ° of haidingerite. iace) normal to L. a =1.590 ±0.003. 0 = 1.602 ±0.003. 7 = 1.638 ±0.003.

HAMLINITE. Eagle Rock mine, Boulder County, Colo. (F. L. Hess). Uniaxial + but shows anomalous birefringence in hexagonal segments. Has zonal growths. co = 1.620 ±0.005. 6=1.630 ±0.005.

HANCOCKITE. Franklin Furnace, N. J. (U. S. N. M. 84995). Optically-, 2V large, p>u (perceptible). Pleochroism rather strong in reddish brown, absorption Z>X. a =1.788 ±0.003. = 1.81 ±0.01. 7 = 1.830 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 83

HANNAYITE. Skip ton Hochla, Ballarat, Victoria (Col. Roebling). White powder or crust. Contains newberyite, hannayite, and other minerals. Op­ tically-, 2E = 69°±2°, 2V = 42°±1° (measured). Dispersion not perceptible. X is perceptibly normal to the perfect cleavage, and Y makes an angle of about 33° with the fibers. These data indicate a monoclinic mineral with X = & and Y Ac = 33° ±. a=1.555±0.003. 0=1.572 ±0.003. 7= 1.575±0.003.

HATCHETTOLITE. Mitchell County, N. C. (Col. Roebling). Isotropic and nearly colorless in section. It is filled with birefracting shreds, probably due to partial alteration. n is variable but averages about 1.98.

HAUERITE. Raddusa, Sicily (A. M. N. H.). Isotropic and deep red in section. Somewhat paler in color than the selenium melt. nLi = 2.69 ±0.01.

HAUSMANNITE. Plumas County, Calif. (U. of C.). Reddish brown in section and nonpleochroic. Uniaxial , tend to lie on a cleavage normal to the optic axis. COL, = 2.46. eLi = 2.15.

HEMAFIBRITE. Nordmark, Sweden (Col. Roebhng). Optically+ , 2V moderate. Red-brown in section and nonpleochroic. a=1.87±0.01. |8=1.88±0.01. 7=1.93±0.01.

HEMATOLITE. Nordmark, Sweden (A. M. N. H.). "Diadelphite." Brownish-red crystals with perfect cleavage. Optically , 2V = small, the hyperbolas of the interference figure open slightly. Colorless to brownish red in section and nonpleochroic. w =1.733 ±0.003. e= 1.714 ±0.003.

HERCYNITE AND PLEOXASTE. 1. Rogers mine, Poughkeepsie, N. Y. (U. S. N. M. 50520). Her- cynite. Black in mass. In section grass-green and filled with inclu­ sions of magnetite (?). Isotropic. n =1.800 ±0.005. 84 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

2. Virginia. Hercynite (or pleonaste, as it contains considerable MgO). Characters similar to those of No. 1. n=1.785±0.005. 3. Peekskill, N. Y. Pleonaste. Material analyzed by G. S. Rog­ ers.27 Contains A1203> 65.02; FeO, 20.28; MgO, 13.70. Characters similar to those of Nos. 1 and 2. 7i=1.775±0.005. The refractive index commonly given for hercynite, 7? = 1.749 (LeVy-Lacroix), is no doubt too low.

HERRENGRUNDITE.

Herrengrund, Hungary (U. S. N. M. 84659). Optically-, 2E = 68°±3°, 2V = 39°±2° (measured), pturquoise green.

HETAEROLITE.

1. Franklin, N. J. (A. M. N. H.). Uniaxial-, tend to lie on basal cleavage, .pleochroism faint in red-brown, absorption e >w. u = 2.34±0.02. = 2.14±0.02. . . Palache gives composition of this mineral as ZnO.Mn2O3 . Specific gravity, 4.85. 2. Leadville, Colo. (G. F. Loughlin). Nearly black fibers. More nearly opaque than the mineral from New Jersey. Uniaxial or nearly so, optically , elongation of fibers is + . w = 2.2G±0.02. e = 2.10±0.02. The indices of refraction are somewhat variable. Ford and Bradley give the composition of hetaerolite from this locality as 2Zn0.2Mn203.H20. Specific gravity, 4.55.

HETEROSITE.

1. La Vilate, France (U. S. N. M. 48622). Optically-, 2V large, variable in properties. Some of the lighter-colored parts have /3 = 1.84; some of the darker have j3 above 1.87. Birefringence 0.03 ±.

2' New York Acad. Sci. Annals, vol. 21, p. 69, 1911. MEASUREMENTS OF OPTICAL PROPERTIES. 85

2. Limoges, France (U. of C.). Nearly black in mass, dark red in powder, more nearly homogeneous than No. 3. Optically , 2V large; lies on a cleavage normal to Bxa =X. Strongly pleochroic. a = 1.86 ± 0.01; greenish gray. /3 = 1.89 ± 0.01; deep red (hematite red). 7 = 1.91 ±0.01; dark red.

HIBBENITE. Salmo, B. C. Type from Prof. Phillips. Optically - , 2E = 92° ± 2°, 2V = 54 ° ± 1 ° (measured), p < v (perceptible). a = 1.582 ±0.003. /3 = 1.592 ±0.003.. 7 = 1.593 ±0.003. X is normal to the most perfect cleavage and Y is parallel to the two cleavages. Compare with Hopeite (p. 87) and Spencerite (p. 135). HIELMITE. 1. Fin Creek, Sweden (A. M. N. H). Optically+, 2V probably small. Nearly opaque, very strongly pleochroic. «Li -2.30 ±0.02; yellowish brown. 7Li = 2.40 ±0.03; nearly opaque. 2. Kararfvet mine, Sweden (U. S. N. M. 14439). Nearly or quite uniaxial, optically+ , strongly pleochroic.

coLi = 2.30 ±0.01; yellowish brown. eu = 2.40 ± 0.04; nearly opaque.

HIGGENSITE. Bisbee, Ariz. Optically , 2V near 90°, p>v rather strong. a = 1.800 ±0.005. 0= 1.831 ±0.005. 7 = 1.846 ±0.005.

HISINGERITE. Riddarhyttan, Sweden (U. S. N. M. 48995). Amorphous and in section the color is zinc-orange. n ranges from 1.49 to 1.53; averages about 1.51,

HODGKINSONITE. Franklin, N. J. (original material from W. T. Schaller). Opti­ cally , 2V moderate, p > v (rather strong). X makes a large angle with the normal to the cleavage. « = 1.715±0.003. 0 = 1.735± 0.003. 7 = 1.75±0.01. 86 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

HOERNESITE. 1. Joachimsthal, Bohemia (A. M. N. H.). White crusts. Fibers similar to No. 2. Optically+ , 2V = 60°±5° (indices). X is normal to the fibers and Z makes an angle of about 31° to the elongation. The fibers tend to lie on face or cleavage normal to X {010} and appear to be monoclinic, with X = &, Z A elongation = 31°. a= 1.563 ±0.003. 0=1.571 ±0.003. 7= 1.596 ±0.003. 2. A specimen labeled Banat, Hungary (Col. Roebling), differs con­ siderably from the specimen described above and is uncertain. Crystals altered to white chalky aggregate of fibers. Optically+ , 2V rather large. a=1.548±0.003. 0=1.556 ±0.003. 7= 1.574 ±0.003.

HOMILITE. 1. Arno, Norway (U. S. N. M. 47031). Isotropic. n=1.640 ±0.005. 2. Langesund, Norway (Brogger, U. of Stockholm). A. Fresh center. Optically+ , 2V large, p>v (rather strong), dispersion of bisectrix perceptible. Pleochroic. a = 1.715 ±0.003; bluish green. 0= 1.725 ±0.003; pale brownish gray. 7 = 1.738 ±0.003; pale smoky gray. B. The altered border has variable optical properties. In thin section it is yellow. The following data for different fragments show the range: (a) Optically+ , 2V small, p>v (very strong). Birefringence about 0.02. /3 = 1.665±0.003. (6) Optically + , 2V very small, p>v (very strong). Birefringence about 0.02. 0=1.660 ±0.003. (c) Optically 4-, 2V = 0. Dispersion very strong. Birefringence about 0.02. 0=1.655±0.005. (d) OpticaUy + , 2E = 78°±5°, 2V = 45°±3°, p

HOPEITE. Broken Hill, Rhodesia (U. S. N. M. 92957). The crystals show the usual zonal structure. Optically , 2E ranges from 0 to 67°. p, ZAC (?) = 44°±. a = 1.586 ±0.003. (3 = 1.598 ±0.003. 7 = 1.605±0.003. 2. Kyan, Calif. Micaceous white mass. 2V very large, probably optically . Y or Z makes a laige angle to the normal to the plates. Plates turned on an edge to give parallel extinction show X along the plates. «= 1.583 ±0.005. /3= 1.596 ±0.005. 7= 1.605 ±0.005. Probably monoclinic tabular {100} or {001}. X = &.

HUEBNERITE. See Wolframite (p. 157). HUEGELITE. Geroldseck, Baden, Germany (Col. Roebling). Yellow needles in mass, tablets and laths in powder. Z is nearly or quite normal to the flat face; interference color on this section is abnormal green, and the extinction in white light is sharp and perceptibly parallel. Other sections show no extinction in white light but give abnormal inter­ ference colors. Optically + , dispersion extreme; for red light 2V is 88 ' MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. small and the optic plane is parallel to the length, whereas for blue the axial angle is large and is across the length. |8= 1.915 ±0.005. Birefringence rather weak. HUMITE.

Monte Somma, Italy. Optically+ , 2V medium large.

a = 1.617 ±0.005. 0 = 1.624 ±0.005. 7 = 1-652 ±0.005.

HUEEAULITE. Branchville, Conn. (W. T. Schaller). Optically-, 2V large, p

HYALOTEKITE. 1. Langban, Sweden (Col. Roebling). 2V very small, optically+ .

a and 0 = 1.960 ± 0.005. 7 = 1.963 ± 0.005.

2. Langban, Sweden (A. M. N. BL). Optically + , 2E = 53°±, 2V = 26° ± (variable) (measured), p < v (strong).

a = 1.965 ±0.003. 0 = 1.965 ±0.003. 7 = 1.969 ±0.003.

HYDROBOEACITE.

1. Stassfurt, Germany (A. M. N. H.). White, chalky mass. Very minute fibers. |3 = 1.626±0.005.

Birefringence 0.01, approximately. Not hydroboracite. 2. Ryan, Calif. Determined as hydroboracite by W. T. Schaller. Acicular aggregates. Two very perfect cleavages parallel to length. Plates parallel to one cleavage show parallel extinction and Y across the length; plates parallel to the other cleavage are sensibly normal to Y and give an extinction angle X to length of 31°. Optically +, 2V rather large, p

HYDBOGIOBERTITE. 1. Philips Springs, Napa County, Calif, (analyzed by R. C. Wells, of U. S. Geol. Survey). Clearly not homogeneous. Successive layers of very minute fibers with some quartz, etc. The material consists chiefly of two fibrous minerals. A. This mineral gives parallel extinction and positive elongation. a =1.52 ±0.01. Birefringence not strong. B. This mineral has a much lower index of refraction and much higher birefringence. The two minerals, A and B, occur in part in separate layers, in part mixed together. 2. Philips Springs, Napa County, Calif. (U. S. N. M. 86673). Not homogeneous. The material consists chiefly of mineral A, but probably some of it is amorphous. Very minutely crystalline. A. Optically +, 2V moderate. Y is normal to the fibers and X A fibers about 20° (?). TI = about 1.52. Birefringence moderate. Probably hydromagnesite. 3. Monte Somma, Italy (Col. Roebling). Not homogeneous. Very finely crystalline material. Chiefly mineral A; some B. A. In this mineral a = 1.52 ±0.01 and y = 1.54 ±0.01. Elongation is + in some crystals and in others. Probably hydromagnesite. B. This mineral has a higher value for n and a lower birefringence. Hydrogiobertite is probably not homogeneous but is an impure hydromagnesite. HYDROMAGNESITE. San Benito County, Calif, (analyzed by R. C. Wells, of U. S. Geol. Survey). Minute fibers. Optically +, 2V moderate. Y parallel to fibers. a =1.527 ±0.003. 0=1.530 ±0.003. 7 = 1.540 ±0.003.

HYDROPHILITE. Artificial mineral made by fusing CaCl2 + H20. 1. Solidified melt, crushed quickly while hot and immersed in oil. Uniaxial +. co =1.605 ±0.005. e=1.615±0.005. It shows a very perfect prismatic cleavage and polysynthetic twinning parallel to the c axis. 2. This material inverts while in the oil to an isotropic form, in which n =1.52 ±0.01, and this material is filled with and bordered by a birefracting material in shreds that has a lower index of refrac­ tion. 90 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

HYDROTALCITE. 1. Snarum, Norway (U. of C.). Basal plates and fibers. Basal cleavage micaceous. Uniaxial . co = 1.516 ±0.003. e=l. 504 ±0.003. 2. Kongsberg, Norway (U. S. N. M. 13191). Characters as in No. 1. Uniaxial . co =1.510 ±0.003. =1.495 ±0.003.' 3. St. Lawrence County, N. Y. (U. S. N. M. 50578). Uniaxial -. co = 1.511 ±0.003. e= 1.496 ±0.003. 4. England. Voelknerite, houghite. Uniaxial . co = 1.553 ±0.003. e= 1.544 ±0.003. This mineral is probably another member of the hydro talcite group.

HYDROZINCITE. 1. Bou-Thaleb mine, Constantine, Algeria (U. S. N. M. 84879). Rather coarse plates and fibers. Optically , 2V = 40° ±2° (indices), p

IDDINGSITE. 1. Pyroxene latite, Wicher Mountain Knoll, Pikes Peak quadrangle, Colo. (U. S. Geol. Survey, P. R. C. 1325). Reddish-brown grains. Optically , 2V large, p

and the axial plane is across a fibrous structure. The indices vary somewhat. a=1.71±0.01. /3=1.74±0.01. 7=1.76±0.01. 2. Basalt, Santa Monica Mountains, Calif. Similar to No. 1. Optical properties vary a little. . /3=1.75±0.01. Birefringence about 0.05. 3. Uncompahgre quadrangle, Colo. (U. S. Geol. Survey, U. P. 17). In thin section clear, pale reddish brown. Optical properties vary a little. Optically+ , 2V large, p>v (strong). Faintly pleochroic. a=1.70±0.01. /3=1.72±0.01. 7=1-74±0.01.

4. Carmelo Bay, Calif. Carmelolite. Original occurrence. The usual reddish-brown grains with a lamellar structure. Optically 2V nearly 90°, p INESITE. Harstig mine, Pajsberg, Sweden (U. S. N. M. 51648). Optically- . 2V = 56°±10° (indices). Sections parallel to the most perfect cleav­ age are nearly normal to Bxa and show Z' to elongation and cross cleavage about 60°. Cleavage section showing emergence of Bx0 on the edge of the field show Y' to the elongation and cleavage about 10°. «= 1.609 ±0.003. /3=1.636±0.003. ' 7= 1.644±0.003. 92 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. Hence, extinction on {010} (Z'Ac) = 60°±, X makes an angle of about 10° with the normal to {010}.

INYOITE. Inyo County, Calif. (Type, W. T. Schaller). Optically-, 2E = 118° ±5°, 2V = 70° ±3° (measured), p

IODYKITE. Old Man mine, Silver City, N. Mex. (U. S. N. M. 48705). Opti­ cally +, bars open slightly. Lie on base. Abnormal green interfer­ ence colors. co = 2.21. = 2.22.

IKON-COPPER CHALCANTHITE. 1. Ducktown, Tenn. (U. S. N. M.). Labeled "Pisanite." Opti­ cally-, 2E = 98°±5°, 2V = 60°±5° (measured), dispersion not no­ ticed. a =1.513±0.005. |8 =1.526± (computed). 7 = 1.534±0.005. 2. Bingham, Utah (U. S. N. M., analyzed). Labeled "Pisanite." In section pale, bluish-green fibers. a=1.515±0.005. 7= 1.536±0.005. 3. Dehydration of artificial pisanite, CuO:FeO = l:l. Finely fibrous. Optically-, 2V moderate, p>v (slight?). a = 1.517±0.003. j8=l:536±0.003. 7 = 1.543 ±0.003.

ISOCLASITE. Joachimsthal (Col. Roebling). White, cotton-like fibers. Minute prisms. Optically+ , angle of Z to elongation small. Section shows parallel extinction normal to X; hence monoclinic, and X = Z>. a=1.565±0.003. /3=1.568±0.003. 7= 1.580±0.003.

JAROSITE. 1. Tintic, Utah, Mammoth mine (Col. Roebling). Reddish-brown cubical crystals. Optically , 2V very small. No good cleavage. Pleochroism perceptible. Indices vary somewhat. a=1.715±0.003; colorless. /3= 1.817 ±0.003; reddish brown. 7 = 1.820 ±0.003; reddish brown. MEASUREMENTS OF OPTICAL PROPERTIES. 93

2. Macon, France (U. S. N. M. 48619). "Carphbsiderite." Soft, straw-yellow powder the grains of which show minute glistening faces. Scales and fibers not very satisfactory for optical study. Optically , and perceptibly uniaxial. Plates {001}. «= 1.81 ±0.01, . e=1.74±0.02.

JEFFERISITE. 1. West Chester, Pa. (U. S. N. M.). Jefferisite. Resembles a pale-brown biotite. Perceptibly uniaxial, optically , optic axis perceptibly normal to the plates. <*= 1.561 ±0.003. Birefringence about 0.02. 2. Lewis, Pa. (U. S. N. M.). Vermiculite. Resembles a pale-green mica. Optically , 2V near 0, Bxa perceptibly normal to plates. 0 and 7 = 1.561 ±0.005. Birefringence about 0.02. 3. Delaware County, Pa. (U. S. N. M.). Jefferisite. Resembles a pale-brown biotite. Optically , 2V very small. j8and7 = 1.557±0.003. Birefringence about 0.02. 4. Corundum Hill, N. C. (U. S. N. M.). Vermiculite. Perceptibly uniaxial, optically . co = 1.560 ±0.005. Birefringence about 0.02.

JEFFERSONITE. 1. Franklin Furnace, N. J. (U. S. N. M.)., Hillebrand's analysis 28 gives SiO2, 51.70; A12O3, 0-36; Fe2O3, 0.37; MnO, 7.43; ZnO, 3.31; CaO, 23.68; MgO, 12.57; Na20, 0.12; H20, 0.65. Optically+ , 2V medium large, p>v (perceptible). a =1.682 ±0.003. 0= 1.690 ±0.003. 7=1.710±0.003. Optic axis nearly normal to cleavage. 2. Franklin Furnace, N. J. Light-brown crystals. Optically-!-, 2V medium large. « = 1.673 ±0.003. 0 = 1.683 ±0.003. 7 = 1.702 ±0.003.

=s Am. Jour. Sci., 4th sor., vol. 7, p. 55, 1899. 94 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. 3. Franklin Furnace, N. J. Black. Optically+ , 2V medium large. Dark green in section. «= 1.720 ±0.003. 0= 1.731 ±0.003. 7= 1-748 ±0.003. 4. Ogdensburg, N. J. (U. S. N. M. 49651). Optically+ , 2V large, p>v (slight). a=1.72±0.01. j8= 1.726 ±0.005. 7=1.74±0.01.

JOHANNITE. 1. Specimens labeled johannite proved to be uranothallite, urano- pilite, gilpinite, and other minerals. 2. Wood mine, Gilpin County, Colo. (Col. Roebling). Green powder. Cryptocrystalline, green in powder. Index of refraction variable. n= 1.70 ±. Birefringence moderate. The data are unsatisfactory, and the mineral is uncertain. JOHNSTRUPITE. Brevig, Norway (Col. Roebling). Optically + , 2V large, p>v (strong). Polysynthetic twinning and very small extinction angle. A poor cleavage nearly normal to Z. a =1.661 ±0.003. 0 = 1.666 ±0.003. 7 = 1.673 ±0.003.

KAINITE.29 Stassfurt, Germany (U. S. N. M.). Colorless mass. Optically F 2V near 90°, p>v (perceptible).

a =1.494 ±0.003. 0= 1.505 ±0.003. 7 = 1.516 ±0.003.

KALINITE AND POTASH ALUM. Two forms of potash alum occur in nature, the one isotropic and the other fibrous and strongly birefracting. As the isotropic variety corresponds to the artificial potash alum it is recommended that the isotropic mineral be called potash alum and that the fibrous bire­ fracting mineral be called kalinite. KALINITE. 1. San Bernardino County, Calif. (Col. Roebling). Chiefly mineral A but contains much B. A. Grains and fibrous aggregates. Optically , uniaxial or nearly so. ______co = 1.456 ±0.003. =1.429 ±0.003. 29 Gorgy, R., Min. pet. Mitt., Band 29, pp. 192-210,1910. The data given by Gorgy are not consistent. MEASUREMENTS OF OPTICAL PROPERTIES. 95

Compare with Mendozite (p. 108). This mineral is probably kalinite. B. Long fibers with large extinction angle. Optically+ (?), 2V is small (?), Z A fibers large. j8 = 1.480 ±0.005. Birefringence weak. Probably pickeringerite or halotrichite. 2. Mount Wingen, Australia (Prof. Lacroix). Clear, coarse fibers. Optically-, 2E = 79°±1°, 2V = 52°±1° (measured). Dis­ persion slight. a = 1.430 ±0.003. 0 = 1.452 ±0.003. 7= 1-458 ±0.003. ; Fibers lying on a face or cleavage sensibly normal to Z show Y to elongation 13°. Probably monoclmic. See Artificial mendozite (p. -). POTASH ALUM. 3. Silver Peak district, Esmeralda County, Nev. . (U. S. N. M. 15768). Glassy grains. Isotropic. ?2 = 1.453 ±0.003. 4. Volcano Lake, south of Imperial Valley, Calif. (U. S. N. M.). Isotropic. n = 1.455 ±0.003.

KALIOPHILITE. Monte Somma, Italy (Harvard). "Fasellite." Uniaxial . w = 1.537 ±0.003. e=1.533 ±0.003.

KEHOEITE. Merrit mine, S. Dak. (Col. Roebling). White, chalky powder. Isotropic. n ranges from about 1.52 to 1.54.

KEILHAUITE. Langesund, Norway (U. S. N. M. 51286). Optically-I-, 2V large, p>v (strong). a =1.915 ±0.005. 0= 1.935 ±0.005. 7 = 2.03±0.01.

KENTROL1TE. L&ngban, Sweden (Yale, B. Coll. 4868). Optically+ , 2V = 90°± (indices), p Y >X. a = 2.10±0.01. 0 = 2.20±0.01. 7 = 2.31±0.02. 96 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

KERMESITE. e> Braunsdorf, Germany (U. S. N. M. 12257). Optically+ , 2V prob­ ably small. Brownish-red needles, clear and translucent, in which Z is perceptibly parallel to the elongation. Birefringence very strong to extreme. < a is a little greater than 2.72. 7 is much greater than 2.72.

** KLEINITE. Teiiingua, Tex. (type material, W. T. Schaller). Optically , 2V small to medium, p < v (very strong). a = 2.16±0.01. 7 = 2.18±0.01. The uniaxial form is optically +. co = 2.19±0.01. e = 2.21±0.01.

KNEBELITE. Dannemora, Sweden (U. S. N. M. 84622). Optically r-, 2V = 60° ± (indices), p>v (strong). «=1.795±0.003. |8= 1.831 ±0.003. 7= 1.842 ±0,003.

KNOPITE. Alno, Sweden (Col. Roebling). In section brownish and indistinctly, | faintly birefracting. n = 2.30.

KNOXVILLITE. See Copiapite (p. 61).

KOECHLINITE. Schneeberg, Saxony. Original material (W. T. Schaller). Opti- ( cally . /3Li = 2.55. Birefringence very strong. ", I KOETTIGITE. Schneeberg, Saxony (Col. Roebling). Fibrous, carmine-red coat­ ing. Optically + , 2V = 77°± (indices), p

KONINCKITE. 1. Vise", Belgium (A. M. N. H.). Pale yellow in powder. Prob­ ably isotropic. 7i=1.65±0.01. Some of the material consists of clouded fibers which have a lower value for n. 2. Richelle, near Vise", Belgium (Col. Roebling). Yellow crust. Chiefly yellow and probably amorphous.

Some colorless fibers have negative elongation. a= 1.645. 7=1-656. See Equeiite (p. 176). KOPPITE. Kaiserstuhl, Baden (Col. Roebling) . In section red to nearly color­ less. Isotropic. n ranges from 2.12 to 2.18.

LAGONITE. Monte Cerbola, Tuscany (Harvard). Mineral somewhat uncer­ tain. Pale yellow and isotropic in section. (variable).

LANAEKITE. Leadhills, Scotland (U. S. N. M. 84657). Plates and fibers. Optically , 2V rather large, p>v (strong), X emerges from the cleavage plates. a=1.93±0.01. /3=1.99±0.01. T = 2.01±0.01.

LANGBANITE. Langban, Sweden (U. S. N. M.). Optically , reddish brown in section and translucent only in thin splinters. Absorption not strong, co > e. coLi = 2.36 ±0.02. 6Li = 2.31±0.02. Some grains are perceptibly isotropic but otherwise similar.

LANGITE. 1. Cornwall, England (U. S. N. M., Shepard Coll. 1244). Bluish green, fibrous crusts. Optically , 2V = 81° (indices), p>v (?) . (rather strong). Laths are normal to X and elongated parallel to Z. Faintly pleochroic in pale green; absorption Z >X. a = 1.708 ±0.005. /3 = 1.760 ±0.005. 7 = 1-798 ±0.005. 32097° 21 7 98 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. Material is not entirely satisfactory. It differs sufficiently from brochantite to distinguish it. Two specimens labeled langite from Klausen, Tyrol, were examined, but they were not langite. 2. Klausen, Tyrol (U. of C.). Not homogeneous. Chiefly a finely fibrous mineral. Optically (?), elongation ; extinction angle not large. « = 1.64±0.02. 7 = 1.86±0.02. Data not very satisfactory. See Tagilite (p. 140). 3. Klausen, Tyrol (U. S. N. M. 52052). Not homogeneous. Chiefly fibers that have the following properties: Pale greenish, optically + , 2V small, elongation+. a =1.552 ±0.005. |8= 1.555 ±0.005. 7 = 1.565 ±0.005.

Perfect cleavage (001) LANTHANITE. Near Bethlehem, Pa. (J. H. U.). Op­ tically-, 2E = 111°±5°, 2V = 63°±3° (measured). Dispersion not noticed. Lie on a face normal to X; hence X = c. a=1.52±0.01. j8= 1.587 ±0.003. 7 = 1.613±0.003. Perfect cleavage(OOl) LARDERELLITE. Larderello, Italy (U. S. N. M. 85174). FIGURE 9. optical orientation of tabular Thin tablets with rhombic outline and an crystals <100> of larderellite. ^ Qf ggo between the edges A veiy perfect cleavage is nearly normal to the plates and bisects the obtuse angle of the rhombs. On these rhombs Z' bisects the acute angle, and Y makes a large angle with the normal to the plates. A fragment lying on the cleavage face is nearly normal to .Z and gives parallel extinction with X parallel to the elongation. Sections turned on one of the crystal faces {Oil} (?) give X' to length 24°. From these data the mineral appears to be monoclinic and if the flat face is assumed to be {100} the cleavage is {001} and the other faces are probably {Oil}, etc. X = &, Z is nearly normal to {001}, and Z A c = 24 ° -I-. A sketch of a crystal is shown in figure 9. Optically +, 2V moderate. a =1.509 ±0.003. 0=1.52±0.01. 7 = 1.561 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 99

LAUBANITE. 1. Wingendorf, near Lauban, Silesia (Mr. Holden). White fibers. Uniaxial + , probably has a perfect prisma'tic cleavage. co =1.475 ±0.003. =1.486 ±0.003. 2. A specimen labeled "Laubanite on natrolite, Winegedocker, Steinbruch, Lauban," from Col. Koebling showed the following properties and is probably bavenite. Interwoven fibers. Opti­ cally +, 2V moderate, p > v (rather strong) (?). a =1.584 ±0.005. 7 =1.588 ±0.005.

LAUTARITE. Tatal, Lautare, Africa (Col. Roebling). Optically +, 2V nearly 90°, p>u (moderate), cleavage piece shows an optic axis emerging on the edge of the field of the microscope. a =1.792 ±0.003. /3= 1.840 ±0.003. 7 =1.888 ±0.003.

LAWRENCITE. Artificial sublimed FeCl3, prepared by Dr. Alien, of the geophysical laboratory of the Carnegie Institution of Washington. Minute hexagonal plates. Uniaxial . co = 1.567 ±0.005. Birefringence rather weak.

LEADHILLITE. Leadhills, Scotland (U. S. N. M. 84486). Optically-, 2E = 17i°±l°, 2VNa = 9°±l° (at 22° C.) (measured), p

LECONTITE. Las Piedras, Honduras (Col. Roebling). Optically , 2E = 60° ±2°, 2V = 40° ± 1 ° (measured), p < v (rather strong). a =1.440 ±0.003. j8 = 1.452 ±0.003. 7= 1.453 ±0.003.

LEPIDOMELANE. Rockport, Mass. (U. S. N. M. 82019). "Cryophyllite." Opti­ cally , 2V nearly 0, green in section. /3 = 1.64±0.01. Birefringence as in biotite. 100 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

LEUCOCHALCITE. Sommerthal, in the Spessart, Germany (U. S. N. M. 46153). White, silky fibers. Optically+ , 2V large, p

LEUCOPHOENICITE. 1. Franklin Furnace, N. J. (U. S. N. M. 84964). In section color­ less. Optically -, 2V = 74° ± 5° (indices), p > v (slight). a = 1.751 ±0.003. |8 = 1.771 ±0.003. 7= 1-782 ±0.003. 2. Franklin Furnace, N. J. (U. S. N. M., Study coll.). Optically-, 2V (large). a =1.760 ±0.005. 0 = 1.778 ±0.005. 7 = 1-790±0.005.

LEUCOSPHENITE.30 Narsarsuk, Greenland. Colorless, tabular, prismatic crystal. X is parallel to the elongation and Y is normal to the tablets. Opti­ cally +, 2V rather large, p > v (rather strong). a = 1.640 ±0.003. ]8 = 1.657 ±0.003. 7 = 1-684 ±0.003.

LEVYNITE. Table Mountain (U. S. N. M.). Uniaxial -. (0 = 1.496. e=1.491.

LEWISITE. Minas Geraes, Brazil (A. M. N. H.). Isotropic, nearly colorless. n = 2.20 ±0.01.

LIBETHENITE. 1. Libethen, Hungary (U. of C.). Dark-green, octahedral crys­ tals. Optically , 2V nearly 90°, p >v (strong). Faintly pleochroic. a = 1.701 ± 0.003; pale blue with a yellowish cast. /3 = 1.743 ± 0.003. 7 = 1.787 ± 0.003; pale blue with a greenish cast. 2. Cornwall, England. Labeled "Olivenite." Optically-, 2V nearly 90°, p>v (strong). Pale green in section and nonpleochroic. a = 1.704 ±0.003. 0 = 1.747 ±0.003. 7 = 1-790 ±0.003. 30 The data of Flink (Meddelelser om Gronland, vol. 24, p. 137,1901) are inconsistent. He was evi­ dently in error in stating that the mineral is optically . MEASUREMENTS OF OPTICAL PROPERTIES. 101

LIEBIGITE. Specimens from Schneeberg, Saxony (U. S. N. M. 45643; Yale, B. Coll. 2995), and from Joachimsthal, Bohemia (A. M. N. H.), proved to be identical with uranothallite. See Uranothallite (p. 151).

LINDACKERITE. Joachimsthal, Bohemia (Col. Roebling). Pale apple-green fibers. Optically +, 2V 73° ± 5° (indices), p

LIROCONITE. Cornwall, England (U. S. N. M. 12567). Optically-, 2V = 72° ± 5° (indices), p

LISKEARDITE. Liskeard, Cornwall, England (A. M. N. H.). Clear, pale-green crust, radiating fibers. Optically + , 2V nearly 90°, Z parallel to elongation. The indices of refraction vary about ±0.01; the values given are near the average. a= 1.661 ±0.005. 0 = 1.675 ±0.005. 7 =1.689 ±0.005.

LITHARGE. See Massicot (p. 105). LIVINGSTONITE. Huitzuco, Mexico (U. of C.). Probably optically , Z parallel to length of prisms. Pleochroism moderate in red with absorption X > Z. aLi = much above 2.72. Birefringence extreme. LOEWIGITE. Zabrze, Upper Silesia (Col. Roebling). Cryptocrystalline. w=1.575±0.01. Birefringence about ±0.01. Compare with Alunite (p. 187). 102 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

LORANDITE. Allchar, Macedonia (U. S. N. M. 83623). Probably optically + , cleaves into needles which have + elongation. Deep red in section. aLl considerably greater than 2.72; shows moderate relief. 7Li much greater than 2.72; shows strong relief. Birefringence extreme. Decomposes in selenium melts unless great care is taken to prevent too high heating. LOSSENITE. Laurium, Greece (U. S. N. M. 84859). Optically+ , 2E = 100° ± 10°, 2V = 50°±5° (measured), p>v (strong). a =1.783 ±0.003. 0 = 1.788 ±0.003. -y = 1.818± 0.003.

LUOINITE. Lucin, Utah (type material from W. T. Schaller). Emerald- green octahedral crystals. Optically-, 2E = 98° ± 2°, 2V = 57° ± 1 ° (measured), p>v (moderate). a =1.563 ±0.003. 0=1.585 ±0.003. 7= 1,592 ±0.003. Compare with Peganite (p. 118).

LUDLAMITE. Cornwall, England (U. S. N. M. 84614). Optically+ , 2V large. a =1.653 ±0.003. 0 = 1.675 ±0.003. 7 = 1.697 ±0.003.

LUDWIGITE AND MAGNESIOLUDW1GITE. 1. Hungary (analyzed, W. T. Schaller). Contains 15.84 per cent FeO. Very dark fibers, strongly pleochroic. Optically + , 2V small, Z = elongation. a and 0= 1.85 ± 0.01; very dark green. 7 = 2.02 ± 0.02; nearly opaque. 2. Morawitza, Banat (Col. Roebling). Black needles. Strongly pleochroic and nearly opaque. Optically + , 2V small, Z parallel to the elongation. a =1.84 ±0.02; dark green. 0 = near a. . 7 = 2.05 ±0.05: dark reddish brown. 3. Head of Big Cottonwood Canyon, Lake mine, near Brighton, Utah (B. S. Butler). Black needles. Strongly pleochroic and nearly opaque. X and Y are greenish, Z is nearly opaque. a =1.85 ±0.01. MEASUREMENTS OF OPTICAL PROPERTIES. 103

Birefringence very strong. 4. Head of Big Cottonwood Canyon, Lake mine, near Brighton, Utah (W. T. Schaller). Black crystals. In section strongly pleo- chroic. Optically + , 2V very small, p>v (extreme). a and 0 =1.83 ± 0.01; bright green. 7 = 1.97 ± 0.01; dark reddish brown. 5. Philipsburg, Mont, (analyzed, W. T. Schaller). Contains 7.27 per cent FeO. Intermediate between ludwigite and magnesiolud- wigite. Black fibers. In section nearly opaque and strongly pleochroic, with absorption 7 >« and 0. |8= 1.86 ±0.01. Birefringence very strong. 6. Magnesioludwigite. Head of Big Cottonwood Canyon, Lake mine, near Brighton, Utah (analyzed, W. T. Schaller). Contains 2.55 per cent FeO. Dark-green fibers. Strongly pleochroic and deeply colored. Optically +, 2V small, elongation +. a and 0 = 1.85 ± 0.01; bright green. 7 = 1.99 ± 0.02; dark reddish brown.

LUENEBURGITE. Liineburg, Germany (U. S. N. M. 85104). Overlapping plates. When turned on edge they lie approxunately parallel to the plane of the optic axes and show a- very large extinction angle. Probably monoclinic with Y = 6. Optically , 2V moderate. a = 1.520 ±0.005. 0=1.54±0.01. 7= 1.545 ±0.005.

MACKINTOSHITE. Llano County, Tex. (Col. Roebling). A dull black cube. Vitreous luster on fresh surface. In powder clear but dusted with black specks, isotropic. n = 1.77 ±0.01.

MAGNESIOLUDWIGITE. See Ludwigite (p. 103). MALACHITE. Copper Queen mine, Ariz. (U. of C.). Optically , 2ENa = 86±3°, 2VNa = 43°±2° (measured), 2V = 39°±2° (indices), p

MANGANITE. 1. Thuringia, Germany (U. of C.). Opaque except in thin splinters. Optically +, 2V small. Cleavage pieces show Y normal to cleavage and Z parallel to the elongation. Slightly pleochroic with absorption Z>X. au = 2.25±0.02; reddish brown. /3Li = 2.25±0.02. 7Li = 2.53±0.02; red-brown. 2. Hungary (U. of C.). Characters as in No. 1. a and/3Li = 2.25±0.01. 3. Markhamsville, Kings County, New Brunswick (U. S. N. M. 45711). Optically+, 2V small, Y normal to cleavage, Z parallel to elongation. Faintly pleochroic in red-brown. Absorption Z>X. «Li = 2.23±0.02. Tu = 2.53±0.02. Manganite is commonly stated to be optically , with Y = c and X = &. The data here given show that it is optically + , with Y = 5 and Z = c. MANGANOSITE. 1. Franklin Furnace, N. J. (Col. Roebling). In section clear emerald-green. Isotropic. n = 2.16±0.01. 2. Nordmark, Sweden (U. S. N. M. 84132). In section clear emerald-green. Isotropic. w=2.16±0.01.

MANGANOSTIBIITE. Nordmark, Sweden (Col. Roebling). Rods and fibers, nearly opaque, with + elongation. Strongly pleochroic. Sections showing X across the length gives perceptibly parallel extinction; other sections show very large extinction angles. Probably monochnic with X = 6. a= 1.92 ±0.02; reddish brown. 7= 1.96 ±0.02; nearly opaque.

- MARGARITE. 1. Chester, Mass. (U. S. N. M. 92834). Coarse pink plates. Optically-, 2E from small to 69°. 2V maximum, 40°. a=1.632±0.003. |8= 1.645 ±0.003. 7= 1.647 ±0.003. 2. Gainesville, Ga. (U. S. Geol. Survey). Fibrous decomposition of corundum. a= 1.632 ±0.003. jS= 1.643 ±0.003. 7= 1.645±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 105

MARGAROSANITE. Franklin Furnace, N. J. (type material from Prof. Ford). Opti­ cally-, 2V = 83°±5° (indices), p

MARIPOSITE. Randsburg, Cain0. (F. L. Hess). Green pleochroic mica. Opti­ cally-, 2V nearly 0. 0=1.63. Birefringence about 0.04. MARTINITE. Curacao, West Indies (F. A. Canfield). Drusy crystals in cavities in replaced gypsum. The crystals are minute tablets with a rhombic outline. The acute angle of the rhombs is about 74°. The acute bisectrix (Z) makes a moderate angle with the normal to the plates, and an optic axis emerges on the edge of the field. Y bisects the obtuse angle of the rhombs. Optically+ , 2V moderately large. The crystals are zoned, and the indices of refraction vary somewhat. j8= 1.605 ±0.01. Birefringence about 0.02. The mineral is probably monoclinic, and the crystal axis 6 bisects the obtuse FIGURE io.-opticai orientation of tab- angle. ofi. the. rhombsi i andi xrY = To. lets {100} of martinite. The more massive part is finely fibrous and has an index of refraction of about 1.59.

MASSICOT AND LITHARGE. Two modifications of artificial plumbic oxide (PbO) have been rec­ ognized; a yellow orthorhombic modification is called massicot and a red tetragonal modification is called litharge. Crystals of natural plumbic oxide that were examined by the author proved to be made up of crystals of the orthorhombic form more or less inverted on the margin of the crystals to the tetragonal modification. It seems best to adopt the names given to the artificial products for the minerals.31

31 In a former paper (Am. Mineralogist, vol. 2,pp. 18-19,1917),the author proposed that the orthorhombic form be called litharge and the tetragonal massicot, but as the most common usage for the artificial products is the opposite of this it is here proposed that the names be interchanged. 106 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

The properties of the two forms, therefore, are as follows: Massicot occurs in yellow orthorhombic, rectangular tablets parallel to {100}. It is biaxial+; X (or possibly Y) is normal to the plates; 2V is large. ft.i = 2.61 ±0.04. Birefringence very strong; specific gravity 9.29. Litharge occurs in red tetragonal tablets parallel to {001}, with a cleavage {110}. It is uniaxial -. wLi = 2.64 ±0.04. Birefringence very strong; specific gravity 9.126. 1. Artificial massicot (assayer's "litharge")- Orange-yellow pow­ der. In plates normal to X (or Y), optically + . Pu = 2.61 ±0.04. Birefringence very strong. 2. Cucamongo Peak, San Bernardino County, Calif. (U. S. N. M. 86525). Brownish orange-red scales, the largest of them 1 milli­ meter across and very soft. Made up of about equal quantities of litharge and massicot. The litharge borders the massicot and is no doubt derived from it. The massicot is nearly colorless in section. Lies on plates normal to X (possibly Y) and is biaxial +. (3 = 2.61 ±0.04. Birefringence strong. The litharge is yellow-orange in section, uniaxial, optically , and has the optic axis normal to the plates. « = 2.64 ±0.02. Birefringence very strong. 3. Austria (U. of C.). White powder of mineral (A), probably a hydrous lead oxide, with a few glistening scales of massicot and litharge (B). A. Very minute fibers, with 7 = 2.03 ±0.03. Some of these show 7 = 2.03, a below 1.97. Compare with Hydrocerusite (p. 202). B. The scales are made up of a core of nearly colorless massicot and an irregular border of red litharge; a paramorph after the massicot. The massicot is nearly colorless in section, optically + , 2V large, /3 much above 2.10, birefringence strong. Plates are normal to X (possibly Y). The litharge is red, uniaxial , with the optic axis perceptibly normal to the plates, w much above 2.10. Birefringence rather strong. 4. Fort Tejon, Kern County, Calif. (U. of C.). "Mennige." Similar to the material from Austria. The massicot is in scales MEASUREMENTS OF OPTICAL PROPERTIES. 107

normal to X (or Y). These show a cleavage or other structure parallel to Y (or X). Tin = 2.62 ±0.04. Birefringence strong. 5. Western Tasmania (U. S. N. M. 84683). Yellow powder. Very finely crystalline to amorphous.

n less than 2.20. Two specimens labeled massicot from Tasmania do not agree with either massicot or litharge. 6. Burden, Tasmania (U. S. N. M. 84620). Canary-yellow powder. Characters like those of No. 5. Some cerusite.

MATLOCKITE. Cramford, Derbyshire, England (U. S. N. M. 80353). Optically-, perceptibly uniaxial.

co = 2.15±0.01. = 2.04±0.01.

MAZAPILITE.

Sec Arseniosiderite (p. 42).

MELANOCEEITE.

1. Langesund, Norway (Prof. Brogger, U. of Stockholm). Dark reddish-brown tabular crystal. Uniaxial , pale yellowish in sec­ tion and nonpleochroic. w=1.73±0.01; varies somewhat. =1.72±0.01; varies somewhat. 2. Langesund fiord, Norway (U. S. N. M. 84329). Completely altered to a reddish-brown isotropic product. n=1.77±0.01. 3. Langesund fiord, Norway (A. M. N. H.). Characters similar to those of No. 2 but contains moderately birefracting fibers,

MELANOPHLOGITE . Racamuto, Sicily (U. S. N. M. 84311). Glassy and isotropic. n= 1.461 ±0.003 in large part. A rather distinct border has n= 1.450 ±0.003. 108 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

MELANOTEKITE. Langban, Sweden (J. H. U.). Black grains. Optically + r 2V = 67°±5° (indices), p

MENDIPITE. Brilon, Westphaha (A. M. N. H.). Nearly colorless, cleavable masses. Optically4-, 2V nearly 90°, p

MENDOZITE. 1. Mendoza, Argentina (Col. Roebling). Minute, interwoven fibers. Apparently uniaxial, optically , elongation . a= 1.431 ±0.003. j8 =1.459 ±0.003. 7 = 1.459 ±0.003. 2. Box Elder County, Utah (F. M. N. H. Chicago). This specimen is made up chiefly of two minerals, A and B. A. Clouded grains. -Optically , 2V very small, dispersion not perceptible. a= 1.434 ±0.003. |8= 1.455 ±0.003. 7=L456±0.003. This material is probably mendozite. B. Laths. On the tabular face they show parallel extinction with Z across the laths. When turned on edge they show Y elongation 30° ±. Optically+ . «=1.484±0.003. 7 = 1.493 ±0.003. This is probably tamarugite. The mineral is probably monoclinic (or triclinic). If the tabular face is taken as {100} the elongation is candZ = &, YAc = 30°. 3. Artificial mendozite. The crystallization of a solution contain­ ing Na2S04 and A12(S03)4 in a desiccator at about 20° C., in about the proportion to form mendozite, gave coarse, pointed, lath-shaped crystals, which had the following optical properties: OpticaUy -, 2E = 85£° ± 1 °, 2V = 56° ± 1 ° (measured). Dispersion slight. a= 1.449 ±0.003. /3= 1.461 ±0.003. 7= 1.463 ±0.003. Crystals that lie on the flat face show parallel extinction and the obtuse bisectrix emerges from the edge of the field. The plane of the optic axis is across the laths. Crystals that are turned on edge give an extinction angle of 30° ±1°. The crystals are therefore MEASUREMENTS OF OPTICAL PROPERTIES. 109 monoclim'c, with the flat face {100} and the elongation c; X = &, YAc = 30°. There is a perfect cleavage {010}. This material differs somewhat from natural mendozite, and it is the same as the artificial monoclinic modification mentioned by Groth.32 On standing in air or in a desiccator these glassy crystals break down in a few days to a white powder which has the following properties: Minute fibers in layers, probably monoclinic with Z = I and a large extinction angle. Optically -f, 2V moderate. a= 1.484 ±0.003. |8= 1.488 ±0.003. 7= 1-499 ±0.003. This material corresponds to tamarugite.

MESITITE. Piedmont (U. S. N. M. 81665). Nearly homogeneous. Uniaxial . co-1.68 ±0.01. Birefringence as in calcite.

MESSEL1TE. Darmstadt, Germany (U. S. N. M. 51823). Optically +, 2V moder­ ate, dispersion not strong. Appears to have a good cleavage, from which an optic axis emerges just out of the field of the microscope. « = 1.644 ±0.003. |8 = 1.653 ±0.003. j = 1.680 ±0.003.

METABKUSIIITE. Sombrero, West Indies (J. H. U.). Optically + , 2V large, Z emerges from the cleavage plates. a =1.535 ±0.005. 0=1.539 ±0.005. 7 = 1.545 ±0.005. This material agrees with brushite.

METAVOLTAITE. 1. Sierra de Caporasee, Chile (Col. Roebling). Canary-yellow powder with voltaite. Under the microscope it is seen to be made up of minute yellow, hexagonal scales. When turned on edge they are birefracting and pleochroic in yellow, with absorption co > e. Optically . co = 1.588 ±0.005. =1.578 ±0.005. 2. Peru (type, Prof. Lacroix). Hexagonal plates, much coarser than No. 1. Uniaxial , strongly pleochroic. co = 1.591 ±0.003; deep orange-yellow. e= 1.573 ±0.003; very pale yellow.

02 Groth, P., Chemische Krystallographie, vol. 3, p. 565,1910. 110 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

MEYERHOFFERITE. Inyo County, Calif. Type material (W. T. Schaller). Colorless. Optically , 2V = 79° ±5° (indices), p>v (perceptible). Extinction on the cleavage plates {010} X'Ac = 33°, on {100} ZAc = 25.3.° a = 1.500±0.003. 0=1.5.35 ±0.003. 7 = 1.560 ±0.003.

MIARGYRITE. Rising Star mine, Idaho (U. of C.). Optically + , 2V moderate, nearly opaque. a>2.72. Birefringence very strong.

MICROLTTE. Amelia, Va. (Univ. of Virginia). Isotropic and colorless in section. n =1.930 ±0.005.

MIEESITE. Broken Hill, New South Wales (Harvard). Pale-greenish crystals. Isotropic with anomalous birefringence. n = 2.20 ±0.02.

MILAE1TE. Granbtinnden, Switzerland (U. S. N. M. 47014). Hexagonal. Optically . w-1.532. Birefringence about 0.003.

MIMETITE. 1. Chihuahua, Mexico (U. S. N. M.). Crystals. Uniaxial , colorless in section. o> = 2.135±0.010. c = 2.120±0.010. 2. Durango, Mexico (U. S. N. M.). Analyzed, pure. Pseudo- morph. The indices vary a little. w = 2.136±0.010. e = 2.122±0.010. 3. Tin tic district, Utah (U. S. N. M. 85013). Optically , pris­ matic crystals. « = 2.14±0.01. e = 2.13±0.01.

MINASRAGRITE. Minasragra, Peru. Type material (U. S. N. M. 87515). Opti­ cally , 2V medium large. Fragments showing X and Z' give par- MEASUREMENTS OF OPTICAL PROPERTIES. Ill allel extinction. Crystals tend to lie on a face or cleavage normal to X. Z makes a small angle with the elongation. Probably mono- clinic, with X = &. Strongly pleochroic. a = 1.518 ± 0.003; deep blue. 0=1.530 ± 0.003; pale blue. 7 = 1.542 ± 0.003; nearly colorless.

MINIUM. 1. Rock mine, Leadville, Colo. (U. S. N. M. 84426). In section very minutely crystalline shreds. Strongly pleochroic. Parallel to the elongation, deep reddish brown; normal to the elongation, nearly colorless. nu = about 2.40. Birefringence weak. Abnormal green interference colors are characteristic. 2. Specimens from a number of other occurrences were examined but gave no better data! MIRABILITE. Carrizo Plains, Calif. Eecrystallized. Optically ,2Vlarge. Dis­ persion of optic axis slight, dispersion of bisectrices strong, and sections normal to Bxa (X) give abnormal interference colors with­ out extinction in white light and show strong crossed dispersion; other sections give sharp extinction. a =1.394 ±0.003. |8 = 1.396 ±0.003. 7= 1.398 ±0.003.

MISENITE. Cape .Misene, Italy (Col. Roebling). Silky fibers. Probably optically + , with a large axial angle. ZA elongation = 33°. a =1.475 ±0.003. 0= 1.480 ±0.003. 7= 1.487±0.003.

MIX1TE. 1. Tintic district, Utah (U. of C.). Minute, bluish-green, acicular crystals. Optically + , 2V nearly or quite 0, extinction perceptibly parallel and elongation +. Pale green in section and nonpleochroic. co = 1.743 ±0.003. e=1.830 ±0.003. 2. Mammoth mine, Tintic,. Utah (U. S. N. M. 48246). Part of type analyzed. Minute green cotton-like fibers. Extinction paral­ lel, elongation+ , pleochroic. Optically + and either uniaxial or with a small axial angle, as the index across the fibers is perceptibly the same for all fibers. co =1.730±0.003; nearly colorless. e=1.810±0.003; bright green. 112 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

MOISSAN1TE. Commercial carborundum. Uniaxial +. «LI = 2.65 ±0.02. Birefringence moderate.

MOLYBDITE. All the specimens examined consist of a canary-yellow powder made up of minute needles which must be optically+ with a small axial angle, as the index of refraction across the length appears to be about the same for all fibers of each specimen. Extinction is par­ allel, Z = elongation. 1. Buena Vista, Colo. a and (3= 1.750±0.01; nearly colorless. 7 = 1.8? approximately; grayish. 2. Hortense, Colo. Similar to No. 1, but a = 1.780. 3. 'Locality 2 miles south of Placerville, Colo. a and |8 = 1.785 ±0.005; nearly colorless. 7 = 2.05 ±0.02; grayish. 4. No locality (U. of C.). Optically+ , 2V = 28° (measured). a =1.720±0.005; colorless. 0 = 1.733±0.005; colorless. 7 = 1.935 ± 0.005; pale canary-yellow. 5. Stuart Ledge, Tuolumne County, Calif. (U. of C.). a = 1.720 ± 0.003; nearly clear and colorless. /3 = 1.73; nearly clear and colorless. 7 = 1.935 ± 0.005; cloudy yellow. 6. Buena Vista, Colo. (U. of C.). a and 0 = 1.72 to 1.76, chiefly 1.745; clear. 7 = 1.94 ±0.01; cloudy yellowish.

MONETITE. Moneta, West Indies (U. S. N. M.). Optically + , 2V moderately large, X emerges from the cleavage. a = 1.515 ±0.003. 0=1.518 ±0.003. 7 = 1.525 ±0.003.

MONTANJTE. Uncle Sam lode, Helena, Mont. (U. S. N. M. 12657). Successive layers of fibers. Optically , 2V small, p

Birefringence about 0.01. Gives very abnormal green interference colors. MONTMOEILLONITE. 1. Millac, France (Prof. Lacroix). Red clay with opaline appear­ ance. Under the microscope it is seen to be rather coarsely crystalline in interwoven fibers. Optical data are not consistent, possibly owing to aggregate effects. The best data indicate an optically mineral with small axial angle, but some fragments seem to be optically + with a large axial angle. 0 = 1.560 ±0.01. Birefringence about 0.02. Compare with Leverrierite (p. 247). 2. Severite. St. Sever, France (Prof. Lacroix). White chalky mass. Mainly isotropic to indistinctly crystalline, but there are a few birefracting shreds. The index of refraction of the main part is 1.548 ±0.005. Montmorillonite is an uncertain species and in common with most of the clay minerals needs further study.

MONTROYDITE. Texas. (Type U. S. N. M. 86637). Probably optically+ , Y (?) normal to very perfect cleavage. Z parallel to the length. The plates could not be turned from this cleavage, and the constants given assume that the cleavage is parallel to the plane of the optic axis. «LI = 2.37 ±0.02. TLI = 2.65 ±0.02. MORDENITE. Morden, Nova Scotia (Col. Roebling). Fibrous mineral. Opti­ cally +. 0 = 1.465. Birefringence about 0.005. MOSESITE. Terlingua, Tex. (Type U. S. N. M.). Pale-yellow crystals. In large part perceptibly isotropic; some crystals show weak bire­ fringence. 71 = 2.065 ±0.010.

NADOE1TE. Djebel-Nador, Constantine, Algeria (U. S. N. M. 84356).

«u= 2.30 ±0.01. 0Li= 2.35 ±0.01. TLI = 2.40 ±0.01. 12097° 21 8 114 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

NAEGITE. Bis mine, Tokyo, Japan (F. L. Hess). The freshest part is clear and isotropic. n =1.818 ±0.005 (varies ±0.01). Compare with Malacon (p. 179).

NANTOKITE. 1. Artificial. Copper foil treated with hydrochloric acid and evaporated to dryness with undissolved copper. The resulting colorless cubic crystals were isotropic. n =1.930 ±0.005. 2. Nantokite from Nantoko, Chile (Col. Roebling), was altered.

NASONITE. Franklin Furnace,^. J. (Yale, B. Coll. 4192). Uniaxial + , tend to lie on a cleavage parallel to the optic axis. co = 1.917 ±0.005. =1.927 ±0.005.

NATROALUNITE. Funeral Range, Calif. (U. S. N. M. 87527). Cryptocrystalline. May be in part amorphous. n =1.568 ±0.003. Birefringence moderate.

NATROJAROSITE. Soda Springs Valley, Esmeralda Valley, Nev. (U. S. N. M. 86932). Hexagonal plates with pyramids. Uniaxial , faintly pleochroic. w = 1.832 ± 0.005; pale yellowish. e = 1 .750 ± 0.005; nearly colorless.

NATRON. Crystals from solution of Na2C03 in water at 22° C. They lose water quickly on exposure to air. Optically , 2V large, p>u (perceptible). a =1.405 ±0.003. j8= 1.425 ±0.003. 7= 1.440 ±0.003. In index liquid (kerosene and fusel oil) the crystals alter rapidly, giving a drop of liquid in which there are good crystals. MEASUREMENTS OF OPTICAL PROPERTIES. 115

NATROPIIILITE. Branchville, Conn. (U. S. N. M.). Optically + , 2E = 170°±10°J 2V = 72°±5° ( measured), p

NEOTANTALITE. Les Colettes d'Allier, France (U. S. N. M. 87017). In section colorless and isotropic. n ranges from 1.95 to 1.99; averages about 1.96.

NEOTOCITE. Sweden (U. S. N. M. 14406). Black, coal-like, brown in powder. In transmitted light brown and in part iso tropic, with n = 1.53 to 1.56; in part birefractory, with ?i = 1.54 to 1.58; birefringence about 0.02. The birefractory part is clearly crystallized from the amorphous part and its variable properties are probably due to incomplete crystallization, giving submicroscopicalty admixed amorphous mate­ rial. The crystalline part is probably bementite. The name neotocite should be confined to the amorphous mineral that has approximately the composition of bementite (MnO.Si02.?iH20). In common with most amorphous minerals, the composition of neotocite is much less definite than is that of the crystalline form, bementite.

NEPTUNITE. San Benito County, Calif. (U. of C.). Optically+ , 2V rather large, p

NEWBERYITE. Skipton Caves, Ballarat, Australia (U. S. N. M. 84341). Opti­ cally+, 2V moderate, p

NEWTONITE. Newton County, Ark. (Col. Roebling). White, chahcy. Made up of very minute square pyramids which have a nearly square outline when lying on the pyramid face. Fragments on a pyramid face show Z' bisecting the acute angle of the rhombic outline, perceptibly uniaxial, optically+ . Probably tetragonal. w =1.560 ±0.005. e=1.580±0.005. 116 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

NITROCALCITE. Artificial, made by drying a solution of calcium nitrate, Ca (N03)2, in a desiccator at room temperature. The result was a crystalline hygroscopic mass. Biaxial-, 2E = 78°±3°, 2V = 50°±2° (meas­ ured) ; dispersion not perceptible. X is normal to a cleavage. a=1.465±0.003. 0=1.498 ±0.003. 7= 1.504±0.003. On further standing in a desiccator dried by freshly ignited calcium chloride the clear crystals of artificial nitrocalcite alter to an isotropic, chalky mass which rapidly changes to the original material on exposure to air. fl,= 1.595 ±0.005.

NITROGLAUBERITE. Atacama, Chile (Col. Roebling). Optically-, 2E = 98°±10°, 2V = 61°±5° (measured), 2V = 68°±3° (indices), p

NITROMAGNE SITE. Madison County, Ky. (Col. Roebling). Optically -, 2E = 7° ± 1 °, 2V = 5°±1° (measured), p

NOCERITE. Nocera, Italy (U. S. N. M. 84152). Uniaxial-, hexagonal cross section. co= 1.512 ±0.003. c=1.487 ±0.003.

OLIVENITE. 1. American Eagle mine, Tintic, Utah (analyzed by W. F. Hille- brand) (U. S. N. M. 83319). OpticaUy + , 2V = 82°±5° (indices), pv (rather strong), and in part optically+ , p

OEPIMENT. Hungary (U. of C.). A cleavage piece showed X normal to the cleavage and Z parallel to the elongation. Optically +. au =2.4 approximately. 0Li = somewhat above 2.72. 7Li = much above 2.72. Birefringence extreme. The data given are not at all satisfactory. OXAMMITE. Guanape, Peru (Col. Roebling). Optically-, 2V = 60°±2° (in­ dices), poxalate, (NH4)2O.C2O3.H2O, show the identity of the two. Optically-, 2V = 61° 44', p

OZOCERITE. No locality (Col. Roebling). Nearly black, waxy mass. Fibrous, elongation negative. Uniaxial +. On crushing, fragments lie on a face normal to the optic axis. w = 1.515 approximately. e = 1.54 approximately. PALAITE. Pala, Calif. Original material (W. T. Schaller). Optically-, 2V rather large, dispersion not perceptible. a = 1.652 ±0.003. 0 = 1.656±0.003. y = 1.660±0.003.

PANBERMITE. See Priceite (p. 122). PARAFFIN. (Col. Roebling). Uniaxial+.. On crushing, the material orients itself normal to the optic axis. co = 1.502 ±0.003. e=1.550 ±0.003.

PARAHOPEITE. Rhodesia, Africa (Col. Roebling). Optically + , 2V very large, p

, P., Chemischo Krystallographie, Teil 3, p. 151, 1910. 118 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

PARALITMINITE. Halle, Germany (A. M. N. H.). Minute, interwoven fibers. Optically , 2V small to 0, X parallel to the elongation. a -1.462 ±0.003. j8= 1.470 ±0.003. 7 = 1.471 ±0.003.

PARTSCHINITE. Olahpian, Transylvania (Col. Koebling). Red, glassy crystals. Colorless in section and isotropic. 7i=1.787±0.003. It is no doubt an ordinary garnet. PECTOLITE. Bergen Hill, N. J. (U. of C.). Optically + , 2V medium large, Z is parallel to the elongation. a = 1.595 ±0.003. 0=1.606 ±0.003. 7 = 1-633 ±0.003.

PEGAN1TE. Striegis, Saxony (J. H. U.). Colorless in section. Optically , 2E = 89°±5°, 2V = 53° ±3° (measured), dispersion not noticed. There is probably a cleavage normal to X and others. Extinction is parallel. a = 1.562 ±0.003. . 0=1.583 ±0.003. 7 = 1.587±0.003.

v PENFIELDITE. Laurium, Greece (Col. Roebling). Colorless. Uniaxial + . co = 2.13±0.01. = 2.21±0.01.

PERCYLITE. No locality (U. of C.). Sky-blue cubes. Sky-blue in section and isotropic. % = 2.05±0.01. Partly altered to boleite. co = 2.06 ±0.01. Birefringence 0.02.

PIIARM ACOSIDERITE. Cornwall, England (U. S. N. M. 45330). Clear, emerald-green crystals. Optically , 2V medium large, p>v (very strong), dis­ persion of bisectrices strong. Emerald-green in powder. The cubes are divided into segments and each of these shows lamellar MEASUREMENTS OF OPTICAL PROPERTIES. 119 twinning parallel to the edges. The extinction angles are large. Some sections show no dispersion of the bisectrices. Probably monoclinic, possibly triclinic. Some fragments are optically +., p

PHOENICOCHROITE. Berezov, Urals (Col. Roebling). Optically +. 2V = medium, p>v (strong). au = 2.34 ±0.02. ftu =2.38 ±0.02. 7Li = 2.65 ±0.02. SeeCrocoite (p. 63). PHOLIDOLITE. Taberg, Sweden (A. M. N. H.). Pale-green chloritic scales. Perceptibly uniaxial , X is normal to the plates. a = 1.503. |8 and 7 = 1.545.

PHOSPHURAN YLITE. Mitchell County, N. C. "From Genth." (Yale.,) Very fine aggregates of yellow plates. Optically , 2V variable but very small, p>v (very strong). Crossed dispersion is strong, X is normal to the plates, strongly pleochroic. a = 1.691 ± 0.003; nearly colorless. ft = 1.720 ± 0.003; canary- yellow. 7 = 1.720 ±0.003; canary-yellow. The mineral is probably monoclinic tabular {010} with X = &. All other specimens examined proved to be autunite.

PICKERINGITE. Peru (U. of C.). Optically -, 2V small to medium. ZAc = 35° on section with strong birefringence. Y = 6. a = 1.476 ±0.003. j8 = 1.480±0.003. 7 = 1-483 ±0.003. Not entirely homogeneous. PICOTITE. Rocklin, Calif. (U. of C.). Isotropic, brownish, translucent only in thin splinters. ft = 2.05 approximately; varies a little. 120 MICEOSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

PICROPHARM ACOLITE. Riechelsdorf, Hessen (Col. Roebling). Optically + , 2E = 68°±3°, 2V = 40°±2° (measured), p

PIEDMONTITE. Pine Mountain, Monterey, Pa. Dark-lavender, coarsely fibrous spherulites. Optically + , 2V = 56°±5° (indices). Strongly pleo- chroic in red. Absorption Z > Y > > X. a =1.758 ±0.003; pale red. 0 = 1.771 ±0.003; deep red. 7 = 1.819 ±0.003; deep red.

PILBARITE. Wodgina district, Australia (U. S. N. M. 87363). Amorphous. n ranges from below 1.73 to 1.76; average 1.74. The isotropic material is filled with minute birefracting bodies with higher index of refraction and strong birefringence.

PINAKIOLITE. Langban, Sweden (U. S. N.M. 85171). Optically -,2E = 69°±2°, 2V = 32°±1° (measured), p

PISANITE. 1. Specimens from Ducktown, Tenn., and from Bingham, Utah, had completely altered to copper-iron chalcanthite. 2. Artificial. Crystallized from a saturated solution with molecu­ lar proportions of ferrous sulphate and cupric sulphate at 4° C. Crystals are pale blue and vitreous in mass and nearly colorless in section. Optically +, 2V very large, dispersion slight. Crystals are rectangular tablets with an angle of about 80°. An optic axis emerges from the tablets at a large angle to the normal to the tablets. Extinction of the tablets is X' Along edge = 22° ±in the obtuse angle. Many crystals show an hour-glass structure. a =1.472 ±0.003. 0 = 1.479 ±0.003. 7= 1.487 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 121

PITTICITE. Freiberg, Saxony (Col. Roebling). Opaline and amorphous, in large part, with a conchoidal fracture. In section the color is reddish brown. : % = 1.635±0.005.

PLANCHEITE. Type material from Kongo, Africa (W. T. Schaller, who procured it from Prof. Lacroix). 1. Minute, interwoven, blue fibers. a = 1.640 ±0.005. y = 1.697±0.005. Elongation +, appears to be uniaxial +, but this appearance may be due to interwoven fibers. 2. Coarser needles from a spherulite. Optically + , 2V medium, elongation+ , X appears to be normal to a cleavage. The indices vary a little. a = 1.645 ±0.005. j8 = 1.660 ±0.005. T=1.715±0.005.

PLATTNERITE. "You Like" lode, Mulian, Idaho (U.S.N.M.). Very unsatisfac­ tory material for optical study, clouded and nearly opaque. No bi­ refringence was recognized. nu = 2.30 ±0.05.

PLEONASTE. See Hercynite (p. 83). PLUMBOGUMMITE. Canton, Ga. (U. S. N. M. 44510). Uniaxial+ , spherulites or suc­ cessive layers of fibers. The indices of refraction vary somewhat and the values given below are about the average. o>= 1.653 ±0.01. e=1.675±0.01.

PLUMBO JAEOSITE. Cooks Peak, N. Mex. (U. S. N. M. 8655). Analyzed. Hexagonal plates. Optically , rather strongly pleochroic. co =1.875±0.005; yellow-brown. e=1.786±0.005; nearly colorless. Some of the plates divide into hexagonal segments that have a small axial angle. 122 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

POLYBASITE. Rudolfschacht, Marienberg, Germany (U. of C.). Optically-, 2E rather small. Dark red in transmitted light. nLi above 2.72. ; Birefringence strong. POLYCRASE. Baringer Hill, Tex. (U. S. N. M.). In section clear brown and per­ ceptibly isotropic. rj,= l.70 ±0.01.

POLYMIGNITE. Frederiksvarn, Norway (U. S. N. M. 12256). Reddish brown in section and perceptibly isotropic. n = 2.22±0.01.

POTASH ALUM. See Kalinite (p. 95).

POWELLITE. Peacock Lode, Seven Devils district, Idaho (U. S. N. M. type of Melville). Very pale greenish-yellow octahedral crystals, uniaxial +. w = 1.967 ±0.005. e = 1.978 ±0.005.

PRICEITE. 1. Curry County, Oreg. (Cal. Min.). White, chalky mass. Nearly homogeneous and made up of very minute shreds and rhombic plates. The angle between the edges of the rhombs measured 58° ±1°. Optically , 2V rather small, X makes a considerable angle with the normal to the plates. In crystals lying on the flat face Y' makes an angle of about 14° with the line bisecting the acute angle of the rhombs. a =1.572 ±0.003. 0 = 1.591 ±0.003. y = 1.594 ±0.003. Priceite must be triclinic in crystal symmetry. 2. Chinan Sar, Rhyndacus River, near Panderma, Turkey (U. S. N. M. 46030). " Pandermite." White chalky mass, entirely homo­ geneous, and made up of shreds and plates somewhat coarser than those of priceite, but the crystals are not so well formed. Optically , 2E = 53°±3°, 2V = 32°±2° (measured),- P

These data show the complete identity of priceite and pandermite. They also show that priceite is distinct from colemanite and establish it as a distinct species. The optical properties of the two species are .given in the following table for comparison:

TABLE 4. Optical properties of priceite and colemanite.

Priceite. Colemanite.

Composition...... 5Ca0.6B203.9H20...... 2Ca0.3B2Oi<.5HsO. Tricliuic...... Monoclinic. +. 2V...... 32°...... 55° 20'. 1.573 1.586 Angl e ft ...... 1. 591 1.592 1.594 1. 614

PROCHLORITE. Waterworks Tunnel, D. C. (analyzed, U. S. N. M. 85875). Green plates. Optically +, 2V small, p< v (rather strong). Z is perceptibly normal to the plates. |8 = 1.605. Birefringence low. PROSOPITE. Altenberg, Saxony (U. of C.). Optically + , 2V rather large, p>v (strong). a = 1.501 ±0.003. 18-1.503 ±0.003. 7 = 1.510±0.003.

PSEUDOBROOKITE. Aranyer Berg, Hungary (U. S. N. M. 47052). In section reddish brown and filled with inclusions. Not very satisfactory for accurate optical data. aLi = 2.38 ±0.02l 7Li= 2.42 ±0.02. PSEUDOM ALACHITE. See Dihydrite (p. 68). PSITTACINITE. See Cuprodescloizite (p. 64).

PUCHERITE. Schneeberg, Saxony (U. S. N. M. 46022). Optically-, 2ENa = 50°± 10°, 2V = 19°±5° (measured), p

PURPURITE. 1. Oxford County, Maine (Col. Roebling). Optically+, 2E = 80°±,2V = 38°± (measured), dispersion very strong, as section nearly normal to an optic axis shows abnormal green interference colors. X is normal to the perfect cleavage. The indices of re­ fraction vary about 0.03. p = 1.92 ±0.02. Birefringence about 0.04. Intensely pleochroic. X = grayish. Y = deep blood-red. Z = deep blood-red. 2. Peru, Maine (U. S. N. M. 16123). Optically+ , 2V moderate, strongly pleochroic. a = 1.85 ±0.02. 0 = 1.86 ±0.02. 7 = 1.92 ±0.02. The indices of refraction vary ±0.06.

PYROAURITE. Langban, Sweden (U. S. N. M. 84148). Colorless, basal plates. Perceptibly uniaxial, optically . w=1.565 ±0.003. Birefringence about 0.01 or perhaps a little less.

PYROCHLORE. Ilmen Mountains, Miask, The Urals (U. S. N. M. 4359). Clean, isotropic grains. 7z,= 1.96 ±0.01.

PYROPHYLLITE. Indian Gulch, Mariposa County, Calif. (U..of C.). Rather coarse, pale-green talclike spherulites. Cleavage pieces are long blades with X normal to the blades and Z parallel to the elongation. Extinc­ tion nearly or quite parallel. Optically , 2E = 94° to 104°, 2V = 53° to 60° (measured), 2V = 59° (indices). Dispersion is slight and probably p > u. a = 1.552 ±0.003. 0 = 1.588 ±0.003. 7 = 1.600 ±0.003.

PYROSMALITE. Nordmark, Sweden (U. of C.). Hexagonal crystals, nearly color­ less in section. Uniaxial . co = 1.675 ±0.003. e=1.636±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 125

PYRRHITE. Azores (U. S. N. M., Shepard Coll. 146r). Reddish crystals. Isotropic. ?j, = 2.16±0.02. Compare with Koppite (p. 97).

QUENSTEDTITE. See Oopiapite (p. 61). QUETENITE. Quetena, Caloma, Chile (Col. Roebling). Optically + , 2E = 50°±5°, 2V = 32°±3° (measured), p>v (rather strong). X (or Y) is nearly normal to the cleavage. Strongly pleochroic. a = 1.530 ±0.003; colorless. 0 = 1.535 ±0.003; colorless. 7 = 1.582 ± 0.003; orange-yellow. See Castanite (p. 53). RAIMONDITE. 1. Province Huancom (Col. Roebling). Hexagonal plates, uniax- ial . Some are divided into six biaxial segments with a uniaxial border. 2V small. co = 1.82 ±0.01. Birefringence strong. This mineral is no doubt jarosite. 2. Laurium, Greece (U. S. N. M. 82629). Earthy. Very minute flakes, uniaxial . co = 1.867 ±0.01. e = 1.79±0.01. This mineral is probably piumbojarosite. A determination of PbO on the impure mineral by R. C. Wells gave 23.8 per cent. Rai- raondite is a doubtful mineral. RASPITE. Broken Hill, New South Wales (U. S. N. M. 84439). Small lath- shaped crystals. Very soft. Very perfect cleavage parallel to lath face. Optically +, 2V nearly 0, crystals lying on lath face show parallel extinction and X' is parallel to the length; an optic axis emerges on the edge of the microscope field across the laths. a = 2.27±0.02. /3 = 2.27±0.02. 7 = 2.30±0.02. As the crystals are tabular {100} and elongated &, with perfect cleavage {100}, the optic orientation is: Y = &, X is oblique to the normal to {100}. 126 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

REALGAR. 1. Rul Island, Wash. (U. of C.). OLI = 2-48 ±0.02. /3Li = 2.60 ±0.02. Tu =2.61 ±0.02. 2. Kurdestan, Persia (U. of C.). Optically , 2V small. 2. '0Ll = 2.59 ±0.02. 7Li =2.61 ±0.02. It decomposes in the sulphur-selenium melts unless heated care­ fully. 3. Allchar, Macedonia, Turkey (U. S. N. M. 83623). Optically , 2VLi = 40° (indices), p>v (very strong), dispersion of bisectrices very strong, pleochroic. «Li = 2.46±0.01; nearly colorless. 0Li = 2.59 ±0.01; nearly colorless. 7Li = 2.61 ±0.01; pale golden yellow.

REDDINGITE. Branchville, Conn. (W. T. Schaller). Optically+ /2E = 70° ±, 2V = 41 ° ± (measured), p > v (rather strong). o = 1.651 ±0.003. 0 = 1.65&±0.003. 7 = 1.683 ±0.003.

REMINGTONITE. Lower California, Mexico (Princeton). Uniaxial ; the indices vary a little. co = i.80±0.01. e=1.55 ±0.02.

RETZIAN. Moss mine, Sweden (Col. Roebling). Optically + ; 2V large, p

RHABDOPHANITE. Salisbury, Conn. (Col. Roebling). Colorless fibers with positive elongation. co-1.654 ±0.003. 6 = 1.703 ±0.003.

RHODONITE. 1. Broken Hill, New South Wales (U. S. N. M. 92911). Opti­ cally , 2V medium. o= 1.733. 0 = 1.740. 7 = 1.744. MEASUREMENTS OF OPTICAL PROPERTIES. 127 2. Fowlerite, Franklin Furnace, N. J. (U. S. N. M. 86796). Opti­ cally +, 2V large. a = 1.726. 0 = 1.730. 7 = 1.737.

RIPIDOLITE. Zlatoust, Siberia (U. S. N. M. 50035). Pale-green plates. Opti- cally + , 2E = 46° to 58°, 2V =28° to 36°, p

RISORITE. Risor, Norway (Col. Roebling). In section light reddish brown and isotropic, n varies from less than 2.04 to more than 2.08, average about 2.05. RIVAITE. Vesuvius, Italy (Col. Roeblmg). A mass of bright-blue fibers. Under the microscope it is seen to be made up of two minerals in approximately equal amounts. One of these minerals is clear and isotropic and has an index of refraction of 1.513 ±0.003. The other occurs in prisms embedded in the isotropic part. These prisms are optically , 2V is small, and the elongation is positive. X is normal to the fibers and the extinction is parallel. «=1.614±0.003. 0 =1.627 ±0.003. 7= 1.628±0.03. These properties are not very different from those of wollastonite. A thin section might show more, but sufficient material for a section was not available. ROEBLINGBTE. Franklin Furnace, N. J. (U. S. N. M. 84364). Very finely fibrous, elongation , optically +, 2V small. a=1.64±0.01. 0=1.64 ±0.01. 7=1.66±0.01.

ROEMERITE. 1. Atacama, Chile (U. S. N. M. 51520). Optically-, 2E = 86°±3°, 2V = 51°±2° (measured), 2V = 53°±3° (indices), p>v (very strong). Dispersion of bisectrices marked and some sections show very abnormal interference colors. a= 1.524 ±0.003. 0= 1.571 ±0.003. 7=1.583±0.003. 128 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

2. "Buckingite," Tierra Amarilla, Chile (Col. Roebling). Pink­ ish-brown vitreous crusts and crystals. Optically , 2E = 73°±5°, 2V = 45°±3° (measured), p>.v (strong), crossed very strong. a= 1.519 ±0.003. 0=1.570 ±0.003. 7= 1.580 ±0.003. In white light sections normal to Y and Z give sharp extinction; sections normal to X give no extinction but very abnormal interfer­ ence colors. ROEPPERITE. Franklin Furnace, N. J. (J. H. U.). Optically-, 2V = 77°±5° (indices), p>v (rather strong). a=1.758±0.003. |8 = 1.786 ±0.003. 7 = 1.804 ±0.003.

ROMEITE. 1. Italy (W. T. Schaller). The crystals are divided into segments corresponding to the faces, and each of these segments shows twin lamellae parallel to the face (or at least the edge of the plates). Probably optically and biaxial, but no satisfactory data could be obtained. 0=1.87 ±0.01. Birefringence moderate to weak. 2. Brazil (W. T. Schaller). "Atopite." Similar to No. 1. n= 1.83 varies±0.01. Birefringence weak. ROSELITE. Schneeberg, Saxony (U. S. N. M. 82403). Optically-!-, 2V moder­ ate, p

ROSENBUSCHITE. 1. Langesund Fjord, Norway (R. M. Wilke, of Palo Alto, Calif.). Cleavable, prismatic crystals. Colorless in section. Optically+ , 2E = 110°±10°, 2V = 58°±5° (measured), Z makes a considerable angle with the normal to the cleavage. a = 1.683 ±0.003. 0 = 1.688 ±0.003. 7-1.712±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 129

2. Skudesundskjout, Langesund, Norway (Prof. Brogger, U. of Stockholm). Brown, radial needles. Optically+ , 2E = 115° ±,2V = 60°±5° (measured), very faintly pleochroic. a =1.682 ±0.003; colorless. |8 = 1.687 ±0.003; pale yellowish. 7=1.710±0.003; pale yellowish.

ROWLANDITE. Llano County, Tex. (U. S. N. M. 83324). In section colorless to very pale green and isotropic. n= 1.725 ±0.003.

EUMPFITE. St. Michael, Austria (U. S. N. M. 85189). Optically+ , 2V nearly or quite 0, optic axis normal to scales. 18=1.587. Birefringence about 0.005.

RUTHERFORDINE. Leukengule, Uruguru Mountains, Morogoro, German East Africa (U. S. N. M. 87362). Yellow cube. Minute, matted fibers. Pale yellow in section. «=1.72±0.01. 7=1.80±0.01.

SALMOITE. See Spencerite (p. 135). SALMONSITE. Pala, Calif, (type material from W. T. Schaller). Optically + 2V very large, p>v (strong), Z is parallel to the fibers. Kather strongly pleochroic. Not entirely homogeneous. a= 1.655±0.005; nearly colorless. j8=1.66±0.01. 7=1.670 ±0.005; orange-yellow.

SAMARSKITE. 1. Tres Piedras, N. Mex. (F. L. Hess). Isotropic and brown in color. 7i = 2.10±. 2. Asheville, N. C. Isotropic. In section dark brown and nearly opaque. n = 2.25±0.02. 12097° 21 9 130 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

SAMIRESITE. Madagascar (Prof. Lacroix) . Golden-yellow, vitreous, crystal with a dull outer part. The more vitreous part in section is nearly colorless and isotropic. In part clear and glassy, in part dull and clouded. The index of refraction ranges from 1.92 to 1.96 and is higher for the clouded part. SAPONITE. 1. Banat, Hungary (J. H. U.). Optically , nearly or quite uniaxial. j8=1.55±0.01.. Birefringence rather strong. 2. Cooks Kitchen, Cornwall, England (Col. Roebling). Very minute fibers.

Birefringence about 0.01.

SARKINITE. Harstig mine, Pajsburg, Sweden (U. S. N. M. 48819). Optically- , 2V very large, dispersion not observed. Z makes an angle of 43 °± to the elongation. a =1.780 ±0.003. 0=1.793 ±0.003. 7= 1.802 ±0.003.

SASSOLITE. Sasso, Italy (U. of C.). Optically , 2V very small, dispersion imperceptible. X is nearly normal to the cleavage and plates. a =1.340 ±0.005. 0= 1.456 ±0.003. 7 = 1.459 ±0.003.

SCHIZOLITE. Kangerdluarsuk, Greenland (Harvard). Optically + , 2V rather large, p

SCHNEEBERGITE. Schneeberg, Austrian Tyrol (W. T. Schaller). ?i = 2.09. Anomalous birefringence low.

SCHORLOMITE. Magnet Cove, Ark. (U. S. N. M. 45263). Reddish brown in section and isotropic. 7i= 1.98 ±0.02; variable. MEASUREMENTS OF OPTICAL PROPERTIES. 131

SCHROECKINGER1TE. 1. Joachims thai, Bohemia (Col. Roebling). Green-yellow coat­ ings of minute, prismatic crystals. Optically , 2E = 70°±, 2V = 40°± (measured), p>v (very strong). The section normal to X is elongated and tabular and gives no extinction in white light but very abnormal interference colors, which are due to extreme crossed dispersion. The crossed dispersion is very striking in the interference figure, and when the mineral is so turned as to give a cross this cross is colored red in one pair of oppo­ site segments and blue or violet in the other pair. Pleochroic. a =1.658 ±0.003; 'colorless. |8= 1.687 ±0.003. 7 = 1.690±0.003; canary-yellow. 2. Joachimsthal (Col. Roebling). Labeled "Uranothallite" but probably the same as No. 1. Small yellow-green prismatic crystals. Lath-shaped crystals show lamellar twinning with the composition plane nearly or quite normal to the section and parallel to the elon­ gation. The extinction on this section ZNa A lamellae = 41° ± ; in white light there is no extinction, owing to the marked dispersion. X is inclined somewhat to the normal to this face. On breaking crystals the fragments tend to line on a face that shows sharp, par­ allel extinction with no dispersion. X is across the length of these crystals and Z (or Y) is much inclined to the normal of this cleavage. More abundant fragments lie on a face normal to X and show lamellar twinning and marked dispersion. One fragment showed two sets of twin lamellae at an angle of 44°. Optically-, 2ENa =110°±5°, 2VNa = 57°±3° (measured), P >v (strong). Crossed dispersion extreme. Pleochroic. a =1.660 ±0.003; colorless. 0= 1.698 ±0.003; canary-yellow. 7 = 1.706 ±0.003; canary-yellov. The properties of the two minerals are similar enough to make it nearly certain that they are the same or at least closely related species. A number of other specimens labeled "schroeckingerite" were examined, but they proved to be uranothallite, or some other uranium mineral. The above mineral does not fit any other species and is probably schroeckingerite. It occurs in prismatic crystals with monoclinic symmetry and cleavages {010} very perfect and {100} perfect. It shows lamellae twinning {100} X = & and ZAc = 41°±. SCHROETTERITE. Tallenggraben (U. S. N. M. 93068). Isotropic and essentially homogeneous. ?i=1.584 ±0.003. 132 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

SCHWARTZEMBERGITE. San Rafael, Sierra Gordo, Bolivia (Col. Roebling). Optically , 2V small; dispersion not noticed. <*Li = 2.25 ±0.02. j8L1 = 2.35 ±0.02. 7ia = 2.36 ±0.02.

SCORODITE. 1. Nassau, Germany (U. S. N. M., Shepard Coll. 1445). Very pale green, glassy crystals. The optical properties vary a little. Opti­ cally+, 2E = 124°±10°, 2V = 62° ±5° (measured), P >v (rather strong). a=1.765±0.01. 0=1.774 ±0.01. 7=1.797±0.01. 2. Red Mountain, Colo. (U. S. N. M. 81190). Pale-greenish, very finely fibrous crusts. /3 = 1.785 ±0.005. Birefringence rather strong. 3. Laurium, Greece (U. S. N. M. 79166). Green crystals, octa­ hedral in habit. Optically+ , 2V moderate, p>v (very strong). 0=1.790 ±0.005. Birefringence 0.03. 4. Laurium, Greece (U. of C.). Green crystals, octahedral in habit. Optically +, 2V = 70° ± 5° (indices), p > v (rather strong). a =1.784 ±0.003. 0 = 1.793 ±0.003. 7= 1.812 ±0.003. 5. Marble Valley, Cornwall, England (U. of C.). Botryoidal coat­ ing of pale-green radiating fibers. Optical properties vary somewhat. Elongation +. Optically , 2V very large, p < v (strong). 7 = 1.74±0.01. Birefringence 0.03 ±. 6. Black Pine, Idaho (collected by E. S. Larsen). (Contains Fe203,34.02; Cr203,0.32; P2O5,4.80; As2O5,44.40; H20-110° C., 5.08; H2O + 110° C., 12.25.) Leek-green botryoidal crusts made up of radiating fibers. Optically +, 2V medium, p > v (strong), inclined ex­ tinction. a= 1.738 ±0.005. 0 = 1.742 ±0.005. 7= 1-765 ±0.005. 7. Cornwall, England (U. S. N. M., Shepard CoU. 1446). Fine bright-green crystals. Optically , 2V nearly 90°; dispersion not per­ ceptible. a=1.810±0.003. 0=1.880 ±0.005. 7= 1.925±0.005. 8. Kuira, Bungo, Japan (U. S. N. M. 87137). Pale-green crystals. Optically+ , 2V = 62°±5° (indices), p>u (strong). a =1.888 ±0.003. 0=1.896 ±0.003. 7=1-915±0.003. MEASUREMENTS OF OPTICAL, PROPERTIES. 133

The eight specimens labeled scorodite and described above prob­ ably represent four distinct species. Specimens 1 to 4 are probably the same species and differ only as much as would be expected from, a small isomorphous replacement of some of the constituents. Speci­ men 6 is a scorodite in which a small amount of P205 replaces As2O5, and specimen 5 has similar optical properties. Specimens 7 and 8, however, are probably different minerals. SENAITE. Minas Geraes, Brazil (Col. Roebling). Nearly opaque. nu = 2.50 ±0.03. Birefringence low. SERPENTINE. 1. Chrysotile asbestos, very low in iron. Grand Canyon, west of Grand Canyon post office, at Capt. Bass mine. Analyzed. Very pale buff, silky fibers. Probably optically + with large axial angle. X 1 cleavage, Z // elongation. a= 1.508 ±0.005. p= 1.512 ±0.005. 7= 1.522 ±0.005. A thin section made in the ordinary way showed a = n of balsam =1.539 ±0.003. This increase in the indices of refraction is probably due to loss of water on heating. 2. Thetford, Canada. Greenish, silky fibers. The fibers are smaller in cross section than are those of the Grand Canyon mineral. Optically +, 2V probably small, Z // elongation. a= 1.542 ±0.005. 7 = 1.552 ±0.005. 3. Lowell, Vt. Greenish, silky fibers. The fibers are smaller in cross section than are those of the Grand Canyon mineral. a= 1.543 ±0.005. 7= 1.555±0.005.

SEKPIERITE. Laurium, Greece (U. S. N. M. 50084). Optically-, 2E = 59°±3°, 2V = 35°±2° (measured), p>v (strong). X is normal to the very perfect cleavage. Pleochroic. a = 1.584 ±0.003; very pale greenish, nearly colorless. /3= 1.642 ±0.003; deep greenish blue. 7 = 1.647 ±0.003; deep greenish blue.

SHATTUCKITE. Bisbee, Ariz. (type, W. T. Schaller). Optically + , 2V very large, fibers showing X and Z give parallel extinction, section showing Y and Z shows a small extinction angle. The mineral is probably monoclinic, with X = & and Z to c small. Pleochroic. a = 1.752 ±0.005; nearly colorless. j3 = 1.782 ±0.005; pale greenish blue. 7=1.815±0.005; deeper greenish blue. 134 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

SICKLERITE. Pala, Calif, (type, W. T. Schaller). Optically-, 2V rather large, p > v (very strong). X is normal to a good cleavage and sections on this cleavage give good extinction in white light indicating little or no dispersion of the bisectrices. The mineral is probably ortho- rhombic. Strongly pleochroic. a= 1.715 ±0.005; deep reddish. 0=1.735±0.005; paler reddish. 7 = 1.745±0.005; very pale reddish.

SIDERONATRITE. Sierra Gorda, Chile (U. S. N. M. 48947). Fibers with perfect cleav­ age parallel to the elongation. X is normal to this cleavage and Z is parallel to the elongation. Optically+ , 2V = 58°±5° (indices), p>u (strong). Pleo­ chroic. a =1.508±0.003; nearly colorless. 0 = 1.525±0.003; very pale amber-yellow. 7 = 1.586 ±0.003; pale amber-yellow. A few of the fibers show 7 about 1.595. The elongation may be taken as c and the cleavage as {100}, and the orientation becomes X = &, Y = &, Z = c.

SIDEROTIL. 1. Pale-greenish powder coating fresh mel- anterite from California. Optically , 2Vrather large, p>v (easily perceptible). FIGURE 11. Optical orienta­ a= 1.528 ±0.003. 0=1.537 ±0.003. tion of tablets {010} of artifi­ cial sodium bicarbonate. 7 = 1.545±0.003. 2. Alteration of artificial melanterite same as above.

SIPYLITE. Amherst, Va. (U. S. N. M. 84388). Isotropic grains, pale brownish red in section. n ranges from about 2.05 to 2.07.

SMITHITE. See Trechmannite (p. 144).

SODIUM BICARBONATE. Artificial "A. & H." baking soda. Optically-, 2V = 75°±2° (indices), p>v (perceptible). In elongated rhombic plates with an MEASUREMENTS OF OPTICAL PROPERTIES. 135 angle of 65° between the sides. Y is normal to the plates and X A longer edge = 20° ± in the obtuse angle of the rhombs. Probably monoclinic, tabular {010}, Y = 6. a= 1.380 ±0.005. 0=1.500 ±0.003. 7 = 1.586 ±0.003.

SPADAITE. Capo di Bove, Rome (Col. Roebling). The material is made up of wollastonite, calcite, and a mineral, probably spadaite, that is amorphous to submicroscopic in crystallization. fl,= 1.53 ±0.01. The material is not entirely satisfactory. ^

SPENCEBITE. Sahno, B. C. (type from Prof. Phillips). Colorless, pearly flakes. Optically-, 2E = 83°±2°, 2V = 49°±2° (measured), p>v (rather strong). X is normal to the plates and a perfect cleavage, and Y is parallel to the two cleavages. «= 1.586 ±0.003. 0=1.600 ±0.003. 7= 1.602 ±0:003. Compare with Hibbenite (p. 85) and Hopeite, a (p. 252) and 0 (p. 251). The mineral contains some spherulites of another mineral, probably an alteration product with + elongation, and a somewhat higher index of refraction. There are also grains of a colorless mineral (salmoite) with the following properties: Optically , 2V moderately large, p>v (perceptible). a =1.645±0.003. 0= 1.683 ±0.003. 7 = 1.695±0.003.

SPHAERITE. Cerhovitz, Bohemia (W. T. Schaller). Spherical masses of white fibers. Optically , 2V large, extinction is parallel or nearly so, and Z is parallel to the elongation. a= 1.562 ±0.003. 0= 1.576±0.003. 7= 1.588 ±0.003.

9 SPHAEROCOB ALTITE. Boleo, near Santa Rosa, Baja California (U. S. N. M. 83337). Uniaxial , almost colorless in section. In general appearance resembles calcite. co =1.855 ±0.005. =1.60±0.01. 136 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

SPODIOSITE. Wermland, Sweden (Col. Roebling). Optically+ , 2V = 69° ±5° (indices), p>v (rather strong). The cleavages are not normal to any of the principal optical directions. A fragment lying on one cleavage showed Z' to trace of other cleavage 35° ±. a= 1.663 ±0.003. /3= 1.674 ±0.003. 7= 1.699 ±0.003. Probably triclinic. STIBICONITE. 1. Kern County, Calif. (Cal. Min.). White, op ah'ne material in concentric spheroidal shells. Under the microscope the grains are in part clear and glassy, in part clouded. All are distinctly isotropic. n ranges from 1.605 to 1.63; average about 1.615. 2. Black Warrior mine, Jackson Canyon, 1£ miles south of Union- ville, Nev. (F. L. Hess). Nearly homogeneous. Isotropic, in part clear, in part somewhat clouded. n = 1.647 ±0.005. 3. Antimony, Garfield County, Utah (U. S. N. M. 77034). Altera­ tion of stibnite. Chiefly clear, glassy, and isotropic. n = 1.69±0.01. Some cloudy, faintly birefracting fibers with + elongation. ?i = 1.67±0.01. 4. No locality. Part of a large crystal of altered stibnite (U. of C.). In large part clear and isotropic. n ranges from 1.720 to 1.740; averages 1.730. Some indistinctly birefracting material. 5. No locality (U. of C.). Labeled "August Harding, 1880." A. Abotryoidal, glassy coating, which consists in part of fibrous crusts with + elongation. Birefringence about 0.01. Consists in part of isotropic material. w=1.77±0.01. B. Pale-yellow botryoidal crusts are similar to A. In the bire­ fracting part n= 1.745 ±0.005. MEASUREMENTS OF OPTICAL PROPERTIES. 137 C. Pseudomorph after crystals of stibnite. (a) In part cloudy and perceptibly isotropic. n = 1.745 ±0.0005. (6) In part clear and isotropic. n = 1.71±0.01. (c) In part birefracting fibers with + elongation. n ranges from 1.71 to 1.75 but is chiefly about 1.72. Birefringence about 0.01. The different substances occur in con­ centric layers. 6. Pima County, Ariz. (U. S. N. M. 80703). Chiefly isotropic but with incipient crystallization. The clear isotropic part has % =1.86 ±0.01. Clouded grains have n up to 1.89. 7. Eureka district, Nev. (A. M. N. H.). Rather coarsely fibrous. n ranges from 1.91 to 1.97 about. Birefringence moderate. See Cervantite. (pp. 54-55).

TABLE 5. Optical data of stibiconite, cervantite, and related hydrous oxides of antimony.

Isotropic types. Specimens labeled stibiconite: Specimens labeled stibiconite Contd. Kern County, Calif...... 1.605-1.63 Unknown locality...... 1.77 Unionville, Nev...... 1.640-1.65 Pima County, Ariz...... 1.85-1.87 Garfield County, Utah.... 1.68 -1.70 Cervantite: Unknown locality...... 1.70 -1.72 Cornwall, England...... 1.86-1.90 Do...... 1.72 -1.74 Kern County, Calif...... 1.97-1.99 Do...... 1.74 -1.75 Do...... 1.98-2.00 Birefracting types. . Specimens labeled stibiconite: Cervantite: Garfield County, Utah (bire­ Western Australia (birefring­ fringence low)...... 1. 67±.01 ence strong)...... 1. 91 Unknown locality (birefring­ Fords Creek, New South Wales ence moderate)...... 1. 71 to 1. 75 (birefringence rather strong).. 1.98 Do...... 1. 745 Utah (birefringence indistinct) 2. 05 Do...... 1.77 Knoppenberg, Austria (bire­ Eureka district, Nev... 1. 91 to 1. 97 fringence faint)...... 2. 06 ±0. 02 The optical data show that the minerals commonly called stibi­ conite and cervantite differ greatly in optical properties and that no doubt they differ also in chemical composition. Certainly, more 138 MICROSCOPIC DETERMINATION OF NONOPAQIJE MINERALS. than two species are included in the material examined. Further connected optical and chemical study on this series is greatly needed. The preceding tables show the range of the optical properties of the specimens examined. The variation in single specimens is not usually greater than is shown in a large number of other minerals. In the iso tropic types there is an almost complete series of values for the index of refraction from 1.60 to 2.00. The data for the bire- fracting types are not so satisfactory, for nearly all were finely crys­ talline, and mixture with amorphous material may have given aggre­ gate effects. However, there seem to be groupings about w=1.75, 7i=1.95, and n = 2.05. STILPNOMELANE. 1. Nassau, Germany (Col. Roebling). Perceptibly uniaxial, opti­ cally , X normal to plates, strongly pleochroic. w = 1.69±0.01; dark brown, nearly opaque. e=1.60±0.01; yellowish. 2. Antwerp, N. Y. (U. of C.). Chalcodite. Nearly or quite uniaxial, optically , pleochroic. co=1.76±0.01; dark red-brown. e=1.63±0.02; pale yellowish. 3. North Carolina (F. A. Canfield). Chalcodite. Dark, red-brown, micaceous aggregates. Nearly uniaxial, optically , Bxa normal to the plates, strongly pleochroic. a=1.65±0.01; pale yellowish. /3 and 7 =1.78±0.01; deep red-brown.

STOLZITE. Broken Hill, New South Wales (U. S. N. M. 84439). Uniaxial-. « = 2.27±0.01. e=2.19±0.01.

STRENGITE. 1. Near Giessen, Germany (U. S. N. M., Shepard Coll. 1109W). Pale pink crystals. Optically-1-, 2V very small, p>v (strong). Fibers show positive elongation. «=1.708±0.01. 0=1.708 ±0.01. T=1.745±0.01. 2. Lexington, Va. (U. S. N. M. 46258). Pale-pink crystals. Optically +, 2ENa = 51 ° ± 2°, 2VNa = 29° ± 1 ° (measured), p < v (very strong). Crystals tend to lie on a face normal to Z. a = 1.730 ±0.003. 0 = 1.732 ±0.003. 7 = 1.762 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 139

3. Stewart mine, Pala, Calif, (analyzed, W. T. Schaller). Blue fibers. Optically , 2V moderate, pleochroic. a =1.697 ±0.005; very pale violet. 0=1.714 ±0.0d5; violet. 7= 1.722±0.005; deep blue. 4. Angelardite, La Vilate, France (Prof; Lacroix). Very finely crystalline. Pleochroic. «= 1.710 ±0.005. 7= 1-730 ±0.005.

STRIGOVITE. Strigovan, Silesia (K. M. Wilke, of Palo Alto, Calif.). Hexagonal plates and fibers. Nearly or quite uniaxial and optically . X is normal to the plates. a=l,65±0.01. Birefringence about 0.02. Strongly pleochroic. X = pale green­ ish. Y and Z = nearly opaque.

STRUEVERITE. 1. Salak North, Kwala Kangsar, Puab, Federated Malay States (Col. Roebling). Probably optically + 0), birefringence probably very strong. Very strongly pleochroic, brown in one direction and dark green and nearly opaque in the other. nu = 2.50 ±0.05. 2. Black Hills, S. Dak. (analyzed, F. L. Hess).. Strongly pleo­ chroic and too nearly opaque for good optical data. X is brown and Z is nearly opaque to greenish. Probably optically , for no sections show the brown absorption in both directions, whereas many show the black. j8L1 = 2.50 ±0.03. Birefringence moderate. SUCCINITE. Baltic region (Col. Roebling). Isotropic. TI= 1.543 ±0.003. SULPHOHALITE. Borax Lake, Calif. (Col. Roebling). Iso tropic. n= 1.454 ±0.002. 140 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

SUSSEXITE. Franklin Furnace, N. J. (U. of C.). Fibrous, optically +', Z par­ allel to elongation, probably orthorhombic. a= 1.541 ±0.003. /3= 1.545 ±0.003. 7 = 1.554±0.003.

SVABITE. Pajsberg, Sweden (Col. Roebling). Uniaxial . co =1.706 ±0.003. e=1.698 ±0.003.

SYMPLESITE. Lobenstein, Voigtland, Germany (A. M. N. H.). Blue fibers. Opti­ cally-, 2H = 97°±1°, 2V = 86i°±l° (measured on Federow stage), p>u (rather strong). The fibers tend to lie on a face or cleavage normal to X, and this section gives an extinction angle Z A elonga­ tion = 31£° ±1°. Fibers turned at 90° to this show parallel extinction. Strongly pleochroic. «=1.635±0.005; deep blue. ]3= 1.668±0.003; nearly colorless.. 7 =1.702 ±0.003; yellowish. SYNADELPHITE. I Nordmark, Sweden (U. S. N. M. 84351). Optically+ , 2V small, faintly pleochroic in dark reddish brown. a=1.86±0.01. /3 = 1.S7±0.01. 7=1.90±0.01.

SZMIKITE. 1. Artificial (MnS04.H20). Optically +, 2V near 90°. a =1.562 ±0.003. /3= 1.595 ±0.003. 7= 1.632 ±0.003. 2. Felsobanya, Hungary (A. M. N. H.). Minute grains or crystals with elongation. It appears to be monoclinic, with Z = 6 and extinction on {010} large. «=1.57±0.01. 7 = 1-62±0.01.

TAGILITE. 1. Nizhni Tagilsk, Russia (Col. Roebling). Very fine fibers with ~ elongation. Optically , 2V small. a=1.69±0.01. j8=1.84±0.01. 7=1.85±0.01. MEASUREMENTS OF OPTICAL PROPERTIES. 141 2. Moravico, Banat (Col. Roebling). Labeled "Veszelyite." Green­ ish-blue spherulitic fibers. Optically-, 2V near 0; X is parallel to the elongation. a =1.685±0.005. ft and j= 1.82±0.005. This mineral is probably tagilite. The data are more accurate than those for No. 1, as the material is coarser. 3. SeeLangite (No. 1) (p. 97).

TAMARUGITE. 1. Cerros Pintados, Tarapaca, Chile (Col. Roebling). Mass of color­ less fibers. Optically+ , 2E = 95°±1°, 2V = 59°±1° (measured), dis­ persion not noticed. Some fragments show polysynthetic twin lamellae with small symmetrical extinction (Z to lamellae), other fibers show rather large extinction angles. «= 1.484 ±0.003. /3= 1.487 ±0.003. 7= 1-496 ±0.003. 2. Box Elder, Utah. See Mendozite (p. 108). 3. Artificial. See Mendozite (p. 109).

TANTALITE. See Columbite (p. 59). TAPIOLITE. Haute-Vienne, France (U. S. N. M. 86267). Uniaxial + , very strongly pleochroic. Specific gravity, 7.4. o>Li = 2.27 ±0.01; pale yellowish or reddish brown. Li = 2.42±0.05; nearly opaque. Compare with Tantalite and Columbite (p. 59).

TARAMELLITE. Italy (Col. Roebling). Optically+ , 2E = 69°±5°, 2V = 40°±3° (measured), p>u (strong). X is normal to the plates. The pleo- chroism is marked. a= 1.770±0.003; pale pinkish, nearly colorless. j8= 1.774 ±0.003; pale pinkish, nearly colorless. 7=1.83±0.02; nearly opaque.

TARBUTTITE. Broken Hill, Bone Cave, Rhodesia (U. S. N. M. 86662). Opti­ cally-, 2E = 82°±5°, 2V = 50°±3° (measured). Dispersion of the 142 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. bisectrices is strong. The dispersion of the optic axis is not great, as one bar shows red on the concave side, the other on the convex side. a= 1.660 ±0.003. j8 = 1.705 ±0.003. 7 = 1.713 ±0.003.

TAVISTOCKITE. Cornwall, England (A. M. N. H.). White spherulites attached to a rock. Optically +, 2V = 74° ±5° (indices). Dispersion not percepti­ ble. Y emerges from the cleavage plates, Z is parallel to the elonga­ tion. «= 1.522 ±0.003. 0=1.530 ±0.003. 7= 1.544±0.003.

TAYLORITE. Guanape, Peru (A. M. N. H.). Optically+ , 2E = 54°±3°, 2V = 36°±2° (measured), p>v (rather strong). a= 1.447 ±0.003. j8= 1.448 ±0.003. 7= 1.459 ±0.003.

TELLURITE. Boulder County, Colo. (Col. Roebling). Nearly colorless plates with a very perfect cleavage and adamantine luster. X is normal to the cleavage. Probably optically+ , pO (moderate), but 2V is so nearly 90° that the test was uncertain. «Ll = 2.00 ±0.05. j3Li = 2.18±0.02. 7L1 = 2.35±0.02.

TENGERITE. Ytterby, Sweden (J. H. U.). White coating, in large part fibers and crystal aggregates, in part it may be amorphous. The crystals are optically +, 2V is large, and X is parallel to the elongation. a=1.555±0.003. . 7= 1-585 ±0.003.

TENNANTITE. Arizona (U. of C.). Isotropic. Translucent only in the thinnest edges of splinters. 7ka>2.72.

TENORITE. Vesuvius, on lava of August, 1875 (U. S. N. M. 13607). Long, lath-shaped crystals which show twinning with the composition plane parallel to the long edge. X, which is probably the Bxa, is oblique to the normal to the plates. On these plates the extinction is X' to the composition plane = 35° ±. Very strongly pleochroic. Absorp- . tion Z > >X. Z is nearly opaque. MEASUREMENTS OF OPTICAL PROPERTIES. 143

n is extreme. The birefringence is probably not extreme, although the thickness of the plates is uncertain.

TEPHROITE. Franklin Furnace, N. J. (U. of C.). Optically-, 2V = large, p>u (perceptible). Nearly colorless in section. a= 1.770 ±0.003. 0= 1.792 ±0.003. 7= 1-804 ±0.003.

TERLINGUAITE. Terlingua, Tex. (U. S. N. M. 86645). Optically-, 2Ered = 57°±3°, 2Vred = 20°±2 0 (measured), p

aLI = 2.35±0.02 /3Li = 2.64±0.02. 7Li = 2.66±0.02.

TETRAIIEDRITE. Kapnik, Hungary (U. of C.). Nearly opaque. Reddish on thin edges of splinters. Isotropic. nLi >2.72.

THENARDITE.33 Searles Lake, Calif. Optically-f, 2V nearly 90°, p>u (per­ ceptible) . «= 1.464 ±0.003. /3= 1.474 ±0.003. ' 7= 1.485±0.003.

THERMON ATRITE. 1. Artificial. Optically-, 2E = 77° (measured), 2V =48°±3°; 2V = 48° (indices) p

a-1.420. /3= 1.506. 7=1.524. In pointed laths, with Y normal to flat face and X parallel to the length. 2. Several specimens that were labeled '' thermonatrite" proved to be trona. THORIANITE. Ceylon (U. S. N. M. 87691). Isotropic. Translucent only on the thinnest edges. n varies somewhat but averages about 2.20.

"Gorgy, R., Zur Kenntnis der Mineralo der Salzlagerstatten: Min. pet. Mitt., vol. 29, p. 202,1910. 144 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

THORITE. 1. Orangite. Landbo, Norway (A. M. N.H.). Isotropic, very pale yellow in section. n=1.683±0.003. On ignition over a blast lamp for half an hour it became darker and clouded but remained isotropic. n= 1.78 ±0.01 (varied). 2. Brevik, Norway (U. S. N. M. 49016). Orange-yellow, a little darker than No. 1. Isotropic. n= 1.693 ±0.003. 3. Langesund Fiord, Norway (R. M. Wilke, of Palo Alto, Calif.). Dark brownish-black vitreous crystals. In section partly nearly colorless n= 1.68 ±0.01, partly reddish brown with variable n, which in some grains is above 1.72. Isotropic in large part; some of the material indistinctly fibrous. 4. Langesund Fiord, Norway (U. S. N. M. 87367). Dark-brownish vitreous fragments. In section reddish brown and perceptibly isotropic. n= 1.686 ±0.005. On ignition over a blast lamp for half an hour it became clouded and dusted with dark specks. In part isotropic. n,= 1.85±. In part birefracting. Uniaxial + . co =1.84 ±0.01. Birefringence about 0.01.

TRECHMANNITE. Binnenthal, Switzerland (U. S. N. M.). Cochineal red. Faintly pleochroic. co = pale reddish. e = clear and nearly colorless. Uniaxial . Birefringence extreme. On heating in sulphur- selenium. melts it inverts to a biaxial form, probably smithite, with the following properties. Optically , 2V moderate, p>v (strong). au = 2.48 ±0.02. j3Li = 2-.58±0.02. Tu = 2.60 ±0.02.

TRICHALCITE. Turginsk, Urals (Col. Roebling). Green plates. In section pale bluish green and nonpleochroic. X is normal to the plates and Y MEASUREMENTS OF OPTICAL PROPERTIES. 145,

is parallel to the elongation. The mineral is probably orthorhombic. Optically -, 2V large. «=1.67±0.01. 0=1.686 ±0.003. 7 = 1-698 ±0.003.

TRIPLOIDITE. Branchville, Conn. (U. S. N. M.). Y is nearly normal to the cleav­ age plates, X = &, ZAc is small. Optically + , 2V moderate, p>v (extreme). Dispersion of bisectrices marked. a= 1.725 ±0.003. 0=1.726 ±0.003. 7=1.730±0.003.

TRIPPKEITE. Copiapo, Chile (Col. Roebling). Blue-green crystals, which break up along the perfect prismatic cleavages into flexible a"sbestos-like fibers. Under the microscope they are pale blue-green in transmitted light and not perceptibly pleochroic. The elongation is positive. Uniaxial +. «=1.900±0.01. « = 2.12±0.01.

TRIPUHYITE. Tripuhy, Brazil (Col. Roebling). Greenish-yellow grains. Opti­ cally+, 2V small, p

TRITOMITE. 1. Brevik, Norway (A. M. N. H.). Pale brownish yellow in sec­ tion and sensibly isotropic. n varies from 1.73 to 1.75. 2. Langesund Fiord, Norway (Yale, B. Coll. xx 4178). Pale pink in section and isotropic. n= 1.757±0.005; nearly or quite homogeneous. 3. Brevik, Norway (Col. Roebling). Brownish in section and isotropic. ^ = 1.74 ±0.01.

TROEGERITE. 1. Schneeberg, Weisser Hirsch mine at Neustadtel, Saxony. With zeunerite. Pale lemon-yellow plates. Optically , 2V very small, X normal to the plates. a =1.585 ±0.005. 0=1.630 ±0.005. 7= 1.630 ±0.005. 12097° 21 10 JL46 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

There are also fibers which tend to lie on a face normal to X and have Z parallel to the elongation. Optically , 2V moderate to small, p < v (very strong). |8= 1.665 ±0.005. Birefringence strong. This mineral no'doubt is uranophane. 2. Schneeberg, Germany (U. S. N. M., Shepard Coll. 144). Orange- yellow powder. Plates that are sensibly uniaxial and optically . No dispersion perceptible, e is normal to the plates. co =1.624 ±0.003. e= 1.580 ±0.005.

TRONA. 1. Searles Lake, Calif. Optically-, 2V = 72°±5° (indices), p

TSCHEFFKINITE. 1. Nelson County, Va. (U. S. N. M. 47569). In section reddish brown with much opaque black material along cracks. In part isotropic and in part strongly birefracting and pleochroic. Probably an alteration product. 2. Bedford County, Va. (Yale, B. Coll. 5687). In part isotropic, with ?i=1.880. In part red-brown and birefracting. Optically , 2V moderate. Pleochroic. X = nearly colorless; Y = pale red-brown; Z = rather dark red-brown. j8 = 1.880 ±0.005, Birefringence about 0.01. The properties are somewhat variable. 3. Madagascar (Prof. Lacroix). Black, vitreous mineral with conchoidal fracture traversed by dull brownish streaks, probably due to alteration. The black, vitreous part was used for optical data. In part isotropic and red-brown in section. n= 1.965±0.01 (varies a little). MEASUREMENTS OF OPTICAL, PROPERTIES. 147

In part optically , 2V small, strongly pleochroic in red-brown with absorption Z > X. /3=1.97±0.01 (varies a little). Birefringence 0.02 ±. TSUMEBITE. Tsumeb, Otavi, German Southwest Africa (Col. Roebling). Opti­ cally+, 2V near 90°, pX. a =1.885 ±0.005. 0= 1.920 ±0.005. 7=1.956±0.005.

TUNGSTITE. Salmo, B. G. (W. T. Schaller). Optically-, 2V rather small, p < v (rather strong). Some material shows rather strong absorption Z>Y>X. a = 2.09±0.02. /3 = 2.24±0.02. T = 2.26±0.02.

TURGITE. 1. Salisbury, Conn. (U. S. N. M. 18330). Black fibers with a red streak. Optically , 2V small. X parallel to the elongation. Absorption faint Z>X. «L1 = 2.50 ±0.02. flu and 71,1 = 2.60±0.02. 2. Sahsbury, Conn. (A. M. N. H.). Fibers with elongation. Optically , 2V small. au = 2.40±0.02. flL1 and 7Li = 2.50 ±0.02.

TYROLITE. Mammoth mine, Tintic district, Utah (U. of C.). Pale-green crystals and plates. Optically -, 2E = 65° ± 5°, 2V = 36° ± 3° (meas­ ured), p>v (strong). Lath-shaped crystals, with X normal to the laths and Y parallel to the elongation. Pleochroic. a =1.694±0.003; pale grass-green. 0=1.726±0.003; pale yellowish green. 7= 1.730 ±0.003; pale grass-green. TYSONITE. Cheyenne Mountain, near Pikes Peak, Colo. (U. S. N. M. 84413). Uniaxial , the basal cleavage is not prominent. w= 1.611 ±0.003. e=1.605±0.003. 148 MICROSCOPIC DETERMINATION OF NONOPAQTJE MINERALS.

TYTJYAMUNITE. 1. Siberia (F. L. Hess). Very finely fibrous. Optically , 2V = moderate, X normal to the plates. 0=1.87±0.01. Birefringence very strong. 2. Eed Creek, Browns Park, Uinta County, Utah (F. L. Hess). The material occurs in minute but well-developed plates in rude, elongated rhombs. X is normal to the plates, and Y is parallel to the long edge of the rhombs. The mineral is orthorhombic. Opti­ cally-, 2E = 70°±3°, 2V = 36°±2° (measured), 2V = 36° (indices), pCarnotite (p. 52).

TJLEXITE. 1. California (U. of C.)'. Optically+ , 2V moderate, X is sensibly normal to the fibers, Y makes an angle of about 23° with the fibers. Probably monoclinic, with X = &. 2. Columbus Marsh, Nev. (F. L. Hess). The usual woolly balls. Optically +, 2V large, X is sensibly normal to the fibers. Y makes an angle of 22° ± with the fibers, but this extinction angle appears to vary considerably. a = 1.491 ±0.003. 0=1.504 ±0.003. 7= 1-521 ±0.003. 3. Teheran, Persia (U. S. N. M. 46215). Minute fibers in which Y is perceptibly parallel to elongation or makes a small extinction angle. Probably optically + with large 2V. a= 1.491 ±0.003. 0 = 1.504 ±0.003. 7= 1-520 ±0.003. 4. Hayesine. Tarapaca, Chile (U. S. N. M. 81705). Minute fibers in which Y is perceptibly parallel to the elongation. a= 1.491 ±0.003. j8= 1.503 ±0.003. -y = 1.520±0.003. The specimens of hayesine from TarapacS. in the museums of Johns Hopkins and Princeton universities are similar but show' extinction angles of 24° and 20°. See Bechilite (p. 45). a= 1.495 ±0.003. 0= 1.508 ±0.003. 7= 1.520 ±0.003. MEASUREMENTS OF OPTICAL, PROPERTIES. 149

UEAOONITE (?). Gilpin County, Colo. (U. S. N. M. 85007). Lemon-yellow powder. Very finely crystalline and nearly homogeneous. Made up of minute fibers and imperfect laths which show perceptibly parallel extinction, positive elongation, and X perceptibly normal to the laths. Opti­ cally +, 2V medium, p < v (strong). a=1.75±0.01. 0=1.79±0.01. 7=1-85±0.01. Probably orthorhombic laths. If the elongation is c and the flat face {100}, then Z = c, Y = Z>, and X = a.

UHANOCHALCITE. Johanngeorgenstadt, Saxony (U. S. N. M. 85178). Grass-green coating. Minute, intermatted fibers with positive elongation and abnormal interference colors. Optically +, 2V small. Very pale colored and faintly pleochroic. a = 1.655; very pale yellowish green. 7 = 1.662; pale greenish yellow. The material is too finely crystalline for satisfactory data.

TJRANOCIRCITE. Falkenstein, Saxony. Yellow-green plates. Optically , 2V small, X normal to the plates, faintly pleochroic. a = 1.610±0.003; nearly colorless. 0 and 7 =1.623 ±0.003; pale canary-yellow. The plates show two sets of twin lamellae at right angles to each other. TJRANOPHANE. 1. Silesia (U. S. N. M. 86707). Optically-, 2V small, p

IIBANOPILITE. 1. Joachimsthal, Bohemia (U. S. N. M. 84651). Orange-yellow powder made up of minute laths and fibers. Pale-yellow in section and not perceptibly pleochroic. Optically+ , 2VNa rather large, p Zippeite (p. 160).

URANOSPHAEBITE. Schneeberg, Saxony (Col. Roebling). Orange-yellow fibrous spherulites. Optically+ , 2V very large, p

URANOSPINITE. 1. Schneeberg, Saxony (Col. Roebling). Pale greenish-yellow scales. Under the microscope these scales are seen to be well- formed, rectangular tablets with faces beveling each of the four edges. They are made up of three different zones. A small green core (A) is present in a few of the crystals and is rather sharply MEASUREMENTS OF OPTICAL PROPERTIES. 151 separated from the rest. It has the form of the main crystal. The main part (B) is yellow and has a moderate axial angle. The border (C), which is not invariably present, is yellow and has a very small axial angle. A. The green core has the following optical properties: Optically , sensibly uniaxial. X is normal to the plates, pleochroic. o)= 1.635±0.003; clear, pale green. e= 1.615±0.003; very pale clouded green. This mineral is probably zeunerite. B. The main part has the following properties: Optically , 2E = 78°±2°, 2V = 46°±1° (measured), p>v (rather strong). X is normal to the plates and Z is parallel to the elongation. Rather strongly pleochroic. a = 1.560±0.003; nearly colorless. 0=1.582±0.003; pale canary-yellow. 7 = 1.587 ±0.003; pale canary-yellow. C. The border has the following properties: Perceptibly uniaxial, optically , e is normal to the plates, pleochroic. ' v (rather strong). Rather strongly pleochroic. «= 1.55±0.01; colorless. 0=1.567±0.003; pale yellow. 7 = 1.572 ±0.003; pale yellow.

URANOTHALLITE. 1. Joachimsthal, Bohemia (Col. Roebling). Yellowish-green crust. Colorless in section. Optically +, 2E = 65° ±3°, 2V = 42°±2° (meas­ ured), p>v (moderate). a= 1.500 ±0.003. 0=1.503 ±0.003. 7= 1.539 ±0.003. 2. Joachimsthal, Bohemia (U. S. N. M. 52057). Optically+ , 2E = 64°±3°, 2V = 41° + 2° (measured), p>v (moderate). X is normal to a cleavage. «= 1.498 ±0.003. 0=1.502 ±0.003. 7 = 1.535 ±0.003. 152 MICKOSOOPIC DETERMINATION OF NONOPAQUE MINERALS.

3. Schneeberg, Saxony (U. S. N. M. 45643). "Liebigite." Opti­ cally+, 2E= 57°+5°, 2V = 37°±3° (measured), p>v (perceptible). a= 1.501 ±0.003. |8= 1.503 ±0.003. 7=1.537±0.003. 4. Schneeberg (Yale, B. Coll. 2.995). "Liebigite." Optically+ , 2V rather small. Lies on face normal to X. N |S= 1.505 ±0.003. Birefringence strong. 5. Joachimsthal, Bohemia (A. M. N. H.). "Liebigite." Opti­ cally +, 2V small, p > v (perceptible). j8= 1.505 ±0.005. Birefringence strong. 6. Joachimsthal, Bohemia (Col. Roebling). Labeled "Voglite." Optically + , 2V small, p>v (perceptible). a = 1.499 ±0.003. 0 = 1.501 ±0.003. 7= 1.540 ±0.003. If any reliance can be placed on the labeling of the specimens it is evident that liebigite and uranothallite are identical.

URBANITE. Langban, Sweden (Mr. Holden). Optically + , 2V large, paugite (p. 225). UTAHITE. Eureka Hill mine, Tintic, Utah (U. S. N. M. 48241). Hexagonal plates. Uniaxial , indices of refraction somewhat variable. co= 1.82 ±0.01. Birefringence strong. This mineral is probably jarosite.

VALENTINITE. Algiers (U. of C.). Fibrous. Optically , 2V small, the blue part of the interference figure crosses, p

VARISCITE. Lucin, Utah (analyzed by W. T. Schaller). Emerald-green, pris­ matic, tabular crystals. In powder nearly colorless, no cleavage noticed. Optically + , 2E = 93°±5°, 2V = 55°±3° (measured), p

Y is normal to the plates and Z is parallel to the elongation. Hence X = a, Y = Z>, and Z = c. VASHEGYITE. Vashegy, Hungary (Col. Roebling). Minute fibers with + elonga­ tion. j8=1.48±0.01. Birefringence about 0.02. Compare with Fischerite (p. 75) and Evansite (p. 172).

VAUQUELINITE. Berezov, Siberia (Col. Roebling). Brownish green, fibrous crusts. Optically , 2V near 0, X is parallel to the fibers. In part nearly colorless, in part pleochroic. a = 2.11 ±0.02; pale green 0 and 7 = 2.22 ±0.02; pale brown.

VESZELYITE. 1. Dognacska, Bohemia (A. M. N. H.). Greenish-blue crystals, rudely octahedral in habit. In section pale greenish blue and not perceptibly pleochroic. Optically+ , 2V = 71°±5° (indices), p

VIVIANITE. MulJica Hill, N. J. (U. S. N. M. 79967). Optically+ , 2V = 85° ±3° (indices), dispersion of bisectrices considerable. X is normal to per­ fect cleavage, intensely pleochroic. a = 1.579±0.003; very deep blue. 0=1.603±0.003; nearly color­ less. 7=1.633 ± 0.003; very pale olive-green or brownish. The data commonly given are inconsistent, as a mineral with .7=1.6267, |8= 1.605.0, a =1.5766 would be optically-, with 2V = 81°. The data of Rosicky 33 agree with those of the author except that Rosicky's data for the indices of refraction and axial angle are not consistent. VOELCKERITE. Ziller-Tal, Switzerland. Uniaxial . « = 1.633 ±0.003. =1.629 ±0.003. 83 Rosicky, V., Acad. Sci. BohSme Bull., vol. 17, No. 28, p. 19, 1908. 154 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

VOGLITE. 1. Joachimsthal, Bohemia. '' Specimen from Vogl'' (Yale). Green plates with a rhombic outline and an angle of about 75° between the edges. X is nearly normal to the plates and Z makes an angle of about 33° with the longer side in the acute angle. When turned on edge these plates show lamellar twinning with small extinction angles. The optical orientation of the plates is shown in figure 12. Opti- cally + , 2ENa = 1040 ±, 2VNa = 60°± (measured), p

VOLBORTHITE. 1. Glenn County, Calif. (U. of C.). Green plates. Z is inclined to the normal to the plates. Optically +, 2V ranges from a large angle to 90°, p > v (very strong). Some is probably optically , 2V near 90° p v (v.ery strong). 2V is 0 for violet, X is nearly normal to the plates. Faintly pleochroic. a = 2.01; nearly colorless. /3 and 7 = 2.02; pale green. MEASUREMENTS OF OPTICAL PROPERTIES. 155

From the preceding data it appears that the mean index of refrac­ tion and the birefringence of volborthite are fairly constant and that it is characterized by very strong dispersion, with p > v about the bisectrix which emerges from the plates. This may be either the .acute ( + ), obtuse ( ), or acute ( ).

VOLTAITE. Sierra de Caporasee, Chile (Col. Roebling). Isotropic, fracture conchoidal, color in section oil green. TO = 1.602 ±0.003. A mineral that has the following optical properties is associated with the voltaite in very fine grains: Uniaxial +. co = 1.530 ±0.003. e=1.537±0.003. Shows very abnormal interference colors. These data are some­ what similar to those of coquimbite and it may be a related mineral. VOLTZITE. Elias mine, Joachimsthal (U. S. N. M. 84641), Bohemia. Compact, colorless, fibrous. Z is parallel to the elongation, uniaxial + . n about 2.03. Birefringence rather strong. In liquids of high index made by dissolving sulphur and arsenic trisulphide in methylene iodide the mineral alters. In a liquid in which TO = 2.20 it alters very slowly, even when hot, but in a liquid in which n = 2.025 it alters very quickly, the elongation remains +, the index of refraction increases, and the birefringence decreases. In a liquid in which TO = 1.91 the grains rapidly become isotropic and liquid drops appear. After the altera­ tion n is above 2.20. In the sulphur-selenium melts the alteration is much less rapid. WALPUEGITE. 1. Joachimsthal, Austria (U. S. N. M. 83971), Yellow plates. X is nearly normal to the plates. Optically , 2V medium large. « = 1.90±0.03. /3 = 2.00±0.03. 7 = 2.05±0.03. 2. Schneeberg, Saxony (Col. Roebling). Tabular crystals con­ taining zonal growths which have variable optical properties. The outline is a parallelogram with an angle of about 66° between the 156 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS. edges. The optical orientation of the plates is shown in figure 13. Optically , 2V = 52° (indices), dispersion slight. X is nearly normal to the plates, which have an extinction angle (Y' Along edge in obtuse angle) of about 12°. Plates turned on the long edge show twinning parallel to the flat face and an extinction angle of about 8°. The main part has fairly constant indices of refraction. a =1.871 ±0.005. 0= 1.975 ±0.005. 7 = 2.005 ±0.005. A clear border shows: = 2.01 ±0.01. = 2.03±0.01.

WAPPLEE1TE.

Joachimsthal, Bohemia (A. M. N. H.). Fibers which tend to lie nearly normal to Z. The ex­ tinction is in part parallel, in part inclined. Optically+ , 2V small. a=1.525±0.005. /3= 1.53 ±0.01. 7 = 1.550±0.005.

WARWICKITE.

Edenrille, Orange County, N. Y. (U. S. N. M. 80720). Optically+ , 2V small but variable, indices of refraction somewhat variable. Pleo- chroic in reddish brown with absorption X>Y>Z. Z normal to the cleavage.

FIGURE 13. Optical orienta­ a=1.806±0.005. j8 = 1.809±0.005. tion of tabular {010} crys­ tals of walpurgite. 7 = 1-830 ±0.005.

WATTEVILLITE.

Bauersburg, Bavaria (Col. Roebling). White bent hairlike crystals. Extinction of fibers is not uniform, X appears parallel to the elonga­ tion in some and normal in others. Some fibers normal to X show a large extinction angle. Optically-, 2E = 76°±5°, 2V-48°±3° (measured), dispersion not perceptible. a =1.435 ±0.003. j8= 1.455 ±0.003. 7= 1.459 ±0.003.

WAVELLITE. Bohemia (U. of C.). Optically+ , 2V large, p>v (perceptible). a = 1.525 ±0.003. 0=1.534 ±0.003. 7= 1-552 ±0.003. MEASUREMENTS OF OPTICAL PROPERTIES. 157

WELLSITE. Cullakanee mine, N. C. (U. S. N. M. 84472). Crystals with zonal growths and complex twinning. One section normal to the composition plane showed symmetrical extinction, and Z' made a small angle to the trace of the composition plane. This angle varied in the different zones. Optically +, 2E = 60° ±, 2V = 39° ±, variable (measured). a= 1.498 ±0.003. 7== 1.503 ±0.003.

WIIKITE. Finland (U. S. N. M. 9416). Isotropic, clouded. Index of re­ fraction varies greatly. Average 72, = 2.0, varies ±0.04.

WOLFRAMITE GROUP. 1. Nugget claim, Rollinsville, Gilpin County, Colo. (F. L. Hess). Ferberite. Black crystals. Nearly opaque, red in thin edges. No pleochroism noticed. j8L1 = 2.40 ±0.03. Birefringence very strong. 2. Cornwall, England (U. of C.). Wolframite. Optically+ , 2V large. Absorption rather strong, Z >X.

.OLI = 2.26 ±0.02. j8ti = 2.32 ±0.02. yu = 2.42 ±0.02. 3. Mariposa County, Calif. (U. of C.). Wolframite. In section darker colored and more nearly opaque than No. 1. «LI = 2.31 ±0.03. TLI = 2.46 ±0.03. 4. South Homestake mine, White Oaks, N. Mex. Type analyzed lor F. L. Hess.34 Huebnerite. Contains only 0.55 per cent of FeO. Optically+ , 2V = 73°±5° (indices). In section brown and olive green, in part nearly opaque. a = 2.17±0.01. 0 = 2.22 ±0.01. 7 = 2.32±0.01.

5. Pony, Mont. (F. L. Hess). Huebnerite. Optically+ , 2Vlarge.

a = 2.20±0.02. 7 = 2.30±0.02.

YTTRIALITE. Barmger Hill, Tex. (U. S. N. M. 85070). In section very pale green and isotropic. Fracture conchoidal. n =1.758 ±0.003.

*«U. S. Geol. Survey Bull. 583, p. 24, analysis 4, 1914. 158 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

YTTROCERITE. 1. Edenville, Orange County, N. Y. (U. S. N. M. 47754). Dark violet-blue cubes. In section pale violet, with the color unevenly distributed. Isotropic. 7J, = 1.434±0.003. 2. Sussex County, N. J. (A. M. N. EL). Dark violet-blue cubes.. In section pale violet, with the color unevenly distributed. Isotropic.. =1.435±0.003.

YTTROCRASITE. Burnet County, Tex. (type from Prof. C. H. Warren). In part isotropic, in part weakly birefracting. n ranges from 2.12 to 2.15.

YTTROTANTALITE. Dillingo Moss, Sweden (Yale, B. Coll. 1854). In section red-browii and isotropic. 7i = 2.15±0.02.

ZARATITE. Wood mine, Texas, Lancaster County, Pa. (U. S. N. M. 12633), Emerald-green opaline material. Isotropic. Banded. In the dif­ ferent bands n ranges from 1.56 to 1.61.

ZEPHARO VICHITE.

Trenic, Bohemia (Col. Roebling). Yellowish. Cryptocrystalline.. n=1.55°±0.01. Birefringence about 0.01 to 0.02. This mineral may be impure wavellite. ZEUNERITE. 1. Schneeberg, Saxony (Col. Roebling). Green crystals, rudely cubic in habit. Uniaxial . Pale green in section. w= 1.643 ±0.003. e=1.623 ±0.003. 2. See Uranospinite (p. 150). 3. SeeVoglite (p. 154). MEASUREMENTS OF OPTICAL PROPERTIES. 159

ZINCALTJMINITE. Laurium, Greece (Col. Roebling). Basal plates and fibers. Uniaxial . co = 1.534 ±0.003. e=1.514±0.003.

ZTNCITE. Franklin Furnace, N. J. (U. of C.). Red cleavage piece, Uni- axial +, in section deep red and not perceptibly pleochroic. co = 2.008 ±0.005. e = 2.029 ±0.005.

ZINKOSITE. Artificial. Made by dissolving metallic zinc in concentrated sulphuric acid and evaporating to dryness. Tabular crystals {001} with rhombic outline and an angle of about 62° between the edges. X bisects the acute angle of the rhombs. Probablyorthorhombic. X = a, Y = 6, Z = c. The optical orientation is shown in figure 14. Optically , 2V medium to small, p

The crystals are probably monoclinic arid tabular and probably have a perfect cleavage after {010}. X = Z>, Z Ac = 32° ±3°. C. The greenish-yellow fibers under the microscope are seen to be laths with sharp extinction, Y A elongation 15° ±. When turned on edge they show very abnormal interference colors and give no extinction in white light. These sections are nearly normal to an optic axis. Optically + , 2VNa moderate, pZIRKELITE. Jacupiranga, Brazil (Col. Roebling). In section clear reddish brown and isotropic. » = 2.19±0.01. I ZUNYITE. Zuni mine, Anvil Mountain, near Silverton, Colo. (type, U. S. N.M.). Clear, colorless crystals. Isotropic. n=1.589 ±0.003. CHAPTER V. TABLES FOR THE DETERMINATION OF MINERALS FROM THEIR OPTICAL PROPERTIES.

ARRANGEMENT OF THE DATA IN THE TABLES. Iii the tables the minerals are divided into six groups isotropic, uniaxial positive, uniaxial negative, biaxial positive, biaxial negative, or optical character unknown. The last group includes only a few minerals, mostly very finely crystalline. As the indices of refraction are the most characteristic and the most easily measured of the optical constants, the minerals in each group are arranged in the order of the intermediate index of refraction, /3. The data for each mineral are arranged along a horizontal line. For biaxial minerals the three left-hand columns show the three indices of refraction in the order a, 7, 0. The birefringence is not given, for i't can be determined by subtracting a from 7. After the indices of refraction the name of the mineral is given, and beneath it the chem­ ical composition in the dualistic form. Then follows the axial angle, 2V, and beneath it the dispersion of the optic axis. Next comes the optical orientation, and beneath it the dispersion of the principal optical directions (bisectrices). The crystal system is next given, and beneath it the crystal habit. The next column shows the cleavage, and the next the color of the mineral in the hand specimen. Then follows the hardness and specific gravity. In the last column, under remarks, is given the group to which the mineral belongs, the solubil­ ity, the fusibility, the pleochroism, twinning, and other properties. For isotropic and uniaxial minerals the arrangement is the same, but some of the columns are omitted. For a few minerals only one index of refraction is known, and the birefringence is then given. The birefringence is said to be weak if it is less than 0.010, moderate if between 0.010 and 0.025, strong if between 0.025 and 0.100, very strong if between 0.100 and 0.200, and extreme if greater than 0.200. The axial angle is said to be small if it is estimated to be less than 30°, moderate if between 30° and 60°, and large if over 60°. The dispersion of the optic axis is said to be perceptible if a good interference figure shows faintly perceptible colored borders, weak if a little more easily seen, moderate if easily seen, strong if the hyperbolas are rather broad, colored bands, and extreme if the colored hyperbolas cover much of the field of the microscope. 12097° 21 11 161 162 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

The attempt has not been made to describe all the phenomena ob­ served under the microscope but rather to give the chief optical con­ stants and any exceptional properties that are not simply manifesta­ tions of these optical constants. For example, the section (010) of a monochnic mineral with strong dispersion of the bisectrices will not give sharp extinction in white light but a succession of abnormal interference colors over an .angle whose width depends upon the strength of dispersion. Minerals that have strong dispersion of the optic axis will give abnormal interference colors in white light on sections nearly normal to an optic axis. In general, abnormal inter­ ference colors are due to strong dispersion. The positions, of the optical directions with relation to cleavage or other crystal direction are easily determined, except in triclinic minerals, if the position of the cleavage and of the principal optical directions in the crystal are known. For example, gypsum has a very perfect cleavage (010) and Y = 6; hence cleavage pieces are parallel to the plane of the optic axes and will show the emergence of Y.

COMPLETENESS OF THE DATA. In the classification and nomenclature of the minerals Dana's "System of Mineralogy" has been followed with few exceptions although that classification is now greatly in need of revision. With the exception of the opaque minerals and a few others that are noted in the index and elsewhere, all the species recognized in l)ana's System, including the first three appendices, are included in the tables as well as a considerable number of minerals not considered species in the system and many subspecies of the better known groups. Some minerals whose optical properties differ in different specimens have been inserted in the tables several tunes. The indices of refrac­ tion of about 20 very rare minerals have been roughly estimated from the chemical composition and specific gravity, and these estimated indices have determined the position of the minerals in the tables. It must be borne in mind that a large number of the minerals are variable in all their properties through isomorphism and solid solution. For most species this variability is within moderate limits, and if the properties of the end members are known those of the intermediate members can be estimated. As yet only a few mineral groups have been systematically studied and for many groups the only available constants are for one or more imperfectly placed intermediate members. Where the data were available the end members are placed in the tables and, in many groups one or more intermediate members. Ultimately it is hoped that all optical measurements will be closely tied to good chemical analyses. The data given in the tables as a rule are commonly for particular speci- TABLES JOB DETERMINATION OF MINERALS. 163 mens, and other specimens, even from the same locality, may differ somewhat in indices of refraction and other properties. If the axial angles is large a comparatively small difference may change the optical character and such minerals should be looked for in both the optically positive and negative groups. For more complete descriptions of the minerals the standard mineralogies should be consulted, particularly Dana's "System of Mineralogy" and Hintze's "Handbuch der Mineralogie."

TABLES. TABLE 6. List of minerals arranged according to their intermediate indices of refraction, 8, and showing their birefringences.

fl Birefringence. ft Birefringence.

Air...... 1.000 0.000 1.475 0.011 TTiorofifr^ (?) 0.000 Carnallitc...... 1.475 0.028 Ice...... ].309 0.004 Alunogen...... 1. 476 0.009 1.328 Creedite...... 1.478 0.024 *DtTnf-nr 1.333 ' 0.000 1.478 0.015 1.339 0.000 1.479 0.004 1.349 0.007 Faujasite ...... 1.48 0. 000± 1.364 Weak. Pisanite ...... 1.479 0.015 1.370 0.000 1.480± 0.002 1 V7& 0.012 (?) 0.01 1.396 0.004 1.480 0.012 1.40 ± Dietrichite...... 1.480 0.013 1. 403± 0.000 Ptilolito...... 1.480 0.004 1. 406± 0.000 Phillipsite...... 1.48 0.003 0.008 1.480 0.027 1.414 0.008 1.480 0.007 1.425 0.035 1.48 0.02 ( 0.000 Hanksite ...... 1.481 0.02 1.427 \ to weak. Darapskite ...... 1.481 0.095 1.434 0.000 1.482 0.004 1.434 0.000 1.482 Opal...... 1. 440± 0.000 1.482 0.013 1.44 0.014 1.483 0.009 1.441 0.030 1.483 0.000 1.448 0.012 1.483 0.012 1.45 1.485 0.000 1.45 0.012 1.486 0.003 1.452 0.013 1. 487 O nn? 1.452 0.028 1.487 0.001 1.454 0.000 1.487 0.012 1.454 0.008 1.487 0.000 Wattevillite...... 1.455 0.024 1.488 0.003 1.455 0.028 Vanthoffite...... 1.488 0.004 1.456 0.119 1.488 0.012 1,456 0.000 1.489 0.025 1.457 0.000 1.49 ± o. ooo 1.458 0.026 1.49 ± 0.000 1.459 0.000 SyMte...... 1.490 0.000 1.46 ± 0.11 1.490 0.012 1.46 0.000 1.49 0.01 Mallardite...... 1.490 0.019 1.461 0.000 Fluellite...... 1.490 0.038 1.461 0.014 1.49 0.005 1.463 0.015 Stellerite...... 1.49 0.011 1.463 0.012 Cyanochroite ...... 1.491 1.464 0. Oil Aphthitalito ...... 1.491 0.008 1.465 0.005 1.492 0.128 1. 470± 0.000 1.495 0.000 1.47 0.03 1.495 0.003 1.47 0.004 1.496 0.009 1.47 0.004 1.496 0.000 1.47 ± 0.000 1.498 0.015 1.47 ± 0.000 1.498 0.039 1.47 0.05 Stilbite...... 1.498 0.006 1.470 0.009 1.499 0.007 1.470 0.025 1.50 1.470 0.010 1.50 0.005 FloMte...... 1.473 0.002 Bilinite...... 1.500 Weak. ; o. 001 Nitroglauberite...... 1.500 0.125 1. 474± 1.5 0.000 Thenardite ...... 1.474 0.021 Lazurite...... 1.50 ± 0.000 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, /3, and showing their birefringences Continued.

ft Birefringence. 0 Birefringence.

1.50 ± 0.000 Hydromagnesite...... 1.530 0.013 1.501 0.015 Milarite ...... 1.532 0.003 1.501 0.114 Quetenite...... 1.532 0.056 Paraffin...... 1 CAO 0.048 Glauberite...... 1.532 0.021 1. 502± 0.021 Echellite...... 1.533 0.015 1 Hfl7 0.039 1.533 0.042 1.503 0.009 Zinc-copper chalcanthite 1.533 0.027 1.503 0.028 1.534 0.048 Ulexite...... 1.504 0.029 1.534 0.068 1.505 0.005 Zincaluminite...... 1.534 0.020 1.505 0.001 Wavellite...... 1.534 0.027 Niter...... 1.505 0.172 Succinite...... 1.535± 0.000 1 nn<; 0.022 1.535 0.000 i ^nfi 0.17 1.535 0.002 1.506 0.104 Bromcarnallite ...... 1.535 Very strong. 1.506 0.011 1.535 0.063 1 V)7 0.039 1.535 0.060 Sulphatic cancrinite .... 1.507 0.007 Iron-copper chalcanthite 1.536 0.026 1.507 0.033 Teschemacherite...... 1.536 0.132 TvpViitp 1. 508 0.000 Kaliophilite...... 1.537 0.004 i fins 0.019 1 <\V7 0.015 1.508 0.041 Apophyllite...... 1.537 0.002 1.509 0.001 1.537 0.01 1.509 0.023 Cordierite...... 1.538 0.006 1.510 0.071 Mellite...... 1.539 0.028 Phillipsite...... 1.51 0.003 1.539 0.002 "Pol-ollf-A 1. 510 0.012 Gismondite...... 1.539 0.008 1.510 0.03 Chalcanthite...... 1.539 0.030 1.510 0.010 1.540 0.030 1.51 0.025 1.54 (?) 1.51. ± 0.000 1.54 ± . 0.000 1.51 Weak. 1.54 0.013± 1.512 0.014 Sulphoborite...... 1.540 0.017 1.514 0.000 Luenebergite ...... 1.54 0.025 1.514 0.003 Leverrierite...... 1.541 0.043 1.515 0.025 Halloysite...... 1.542± 0.000 1.515 0.006 1 1149 0.004 1.516 0.046 1.542 0.026 1.516 0.079 1.542 0.130 1.517 0.000 1.543 0.008 1.517 0.000 Halite...... 1.544 0.000 1.517 0.018 Quartz...... 1.544 0.009 1.518 0.003 Pholidolite...... 1.545 0.042 1.518 0.017 1.545 Low. Leiflte...... 1.518 0.004 1.545 0.01 1.518 0.010 1.545 0.013 Newberyite 1.518 0.019 1.545 0.012 1.519 0.007 Hyalophane...... 1.545 0.005 1.52 ± 0.000 1.546 0.008 1.52 0.000 1.547 0.023 1.52 0.051 1.547 0.060± 1.520 0.033 1.547 0.156 1.52 0.03 1.548 0.028 1.52 Weak. 1.549 0.016 1.52 ' 0.008 Cobalt chalcanthite. .... 1.549 0.021 1.52 0.010 1.550 0.006 1 V> 4- 1.55 ± 0.000 1 19 0.004 1.55 0.02 1.521 0.008 1.55 0.02± 1.522 0.005 Mizzonite (MarbMea). . . . 1.551 0.013 1.522 0.009 NarsarsuMte ...... 1.553 0.031 1.523 0.010 Andesine ...... 1.553 0.007 1.523 0.012 1.554 0.016 1.523 0.070 1.555 0.000 1.524 0.028 Soumansite...... 1.555 (?) 1.524 0.012 1.555 0.01 1.524 0.008 Rhomboclase...... 1.555 0.102 1.525 0.000 Whewellite...... 1.555 0.159 1.525 0.078 1.555 0.007 1.525 0.030 1.556 0.009 1.526 0.042 1.56 Weak. 1.526 0.008 Ferrinatrite ...... 1.558 0.053 Albite...... 1.529 0.011 Variscite ...... 1.558 0.031 1.529± 0.066 Beryllonite ...... 1.558 0.009 1 190 0.008 1.559 0.021 1.53 ± 0.000 1.559 0.008 TvfihOGitG 1.53 ± 0.000 1.560 0.020 1.530 0.022 1.560 0.02 Tlacitft Colerainite ...... 1.56 Weak. WappJerite...... i.53 0.025 Humboldtine...... 1.561 0.198 TABLES FOR DETERMINATION OF MINERALS. 165

TABLE 6. List of minerals arranged according^ to their intermediate indices of refraction, j8, and showing their birefringences Continued.

/» Birefringence. /3 Birefringence.

1.56 Moderate. 1.59 ± 0.000 0.000 Collophanite...... 1.59 ± 0.000 1.562 0.011 Chloromanganokalitc . . . 1.59 Very weak. Polyhalite...... 1.562 0.019 Gonnaritc...... >..... 1.59 ± 0.03 1.563 0.009 1.59 Low. Kaolinite...... 1.565 0.006 1.59 0.012 1.565 0.010 a Hopeite ...... 1.59 0.018 1. 565 0.005 1. 590 0.020 1.565± 0.01 1.590 0.033 Elpidite...... 1.565 0.014 Diabantite ...... 1.59 0.055 Gibbsite...... 1.'566 0.021 Metavoltaitc...... 1.591 0.018 Wernerite (MauMeso) 1.567 0.022 1.591 0.071 1.568 0.000 1.591 0.022 1.568 1 0. 015 1.592 0.011 1.569 0.004 1.592 0.036 Griffithite...... 1.569 0.087 Colemanitc ...... 1.592 0.028 Torbemite...... 1.592 0.010 1 <;? Amblygonite ...... 1.593 0.018 Zaratite...... 1.57 ± 0.000 1.594 0.04 1.57 ± 0.000 Astrolite...... 1.594 0. 027 ' 1.57 Weak. Fuchsite...... 1.594 0.04 Phlllipsite...... 1.57 0.010 1.595 0.010 1.57 0.030 Szmikite...... 1.595 0.070 1.570 0.013 1.595 0.012 1.57 ± 0.025 Leucophanite...... 1.595 0.027 1.570 0.011 Gilpinite...... 1. 596 0.036 Nitrobarlte...... 1.571 0.000 1 597 0.037 1.571 0.033 1.597 0.023 1.571 0.059 1.597 0.007 1.572 0.020 1.597 0. 015 1.572 0.020 1.598 0.045 1.572 0.010 1.598 0.019 1.574 0.02 Bervl (high in alkalies) . 1.598 0.008 1.574 0.033 Stib'iconite...... 1.60 ± 0.000 1.575 0.01 Biotite...... 1.600 Strong. 1.575 0.024 1.60 0.033 1.555 0.005 1.600 0.045 1.576 0.003 Chloraluminite ...... 1.60 0.053 1.576 0.043 Spence-ite...... 1.600 0.016 .A-UCClltC 1.576 0.014 Zinnwalditc ...... 1.60 0.03 1.576 0.026 Riversidite ...... 1.600 0.008 1.578 0.057 Paragonite...... 1.60 0.03 1.579 0.002 Borickito...... 1.60 ± 0.000 1.579 0.005 Haidingerite...... 1.602 0.048 1.580' 0.009 1. 603 0.021 1.58 0.03 1.603 0.014 Ripidolite...... 1.580 0.009 Vivianite...... 1.603 0.054 (?) 0. 014 1.604 0.011 1.58 0.03 Voltaite...... 1.604 0.000 ( Rather Prochtorite ...... 1. 605 Low. 1.58 ± \ strong. Martinite ...... 1.605 0.02 1.580 0.008 1.605 0.023 Beryl (low in alkalies) . . 1.581 0.006 1.605 0.100 1.582 0.028 1.606 0.044 1.582 0.008 1.606 0.039 Wernerito (MassMers). . . 1.582 0.031 Eudialyte...... 1.606 0.005 Chrome clinochlore. .... 1.582 0.011 1.607 0.006 1. 582 0.063 Dahllite...... 1.608 0.004 1.582 0.027 1.61 0.025 1 583 0.019 1.61 0.007 Eakleite...... 1.583 0.010 1.61 ± 0.000 1. 583 0. 025 Piadochite...... 1.61 ± 0.000 1.583 0.02 ± Collophanite...... 1.61 ± 0.000 1.584 0.012 1.61 ± 0.000 1.584 0.000 1.611 0.020 1.585 0.01 Meliphanite...... 1.612 0.019 1.585 0.025 1.612 0.004 1.585 0. 013 1.612 0.029 1.585 0.029 1.613 0.047 1.585 mod. 1.613 0.010 1.586 0.011 1.615 0.005 1.587 0.09 1.617 0.022 1.587 Low. 1.617 0.067 1.587 0.251 1.619 0.030 1.588 0.048 1.619 0.014 1.589 0.050 1.62 0.04 1.589 0.011 1.62 0. 015 1.589 0.010 1.620 0.019 1.589 0.001 1.620 0.008 1.689 0.000 1.620 0.034 Zaratite...... 1.59 ± 0.000 Bisbeeite ...... 1.620 0.10 166 MICKOSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, 0, and showing their birefringences Continued.

P Birefringence. P Birefringence.

1 A9 0.002± 1.65 0.03 1.621 0.002 Chloropal...... 1.65 0.03 1.621 0.003 Epistolite...... 1.650 0.072 1.623 0.010 1.652 0.063 1.623 0.026 Datolite ...... 1.653 0.044 1 fi91 0.013 1.653 0.008 1.624 0.009 Messelite...... 1.653 0.040 1.625 0.050 1.654 0.07 1.625 0.010 1.654 0.013 1.625 Jadeite...... 1.654 0.029 1.625 0.023 1.654 0.009 1.625 Wont 1.654 0.053 1.625 0. 037± 1.654 0.016 1.625 1.654 0.022 1.625 Weak. 1.654 0.049 1.626 0.021 Wilkeite...... 1.655 0.005 1.626 0.033 1.655 0.029 1. 627 0. 025 1.655 0.007 Troescritc 1.627 0.045 1.655 0.019 1.628 0.008 1.656 0.008 1.629 0.015 Natrochalcite...... 1.656 0.065 1.63 ± 0.03 1.656 0.03 Homilitc (altered )...... 1.63 0.02 Reddmgite...... 1.656 0.032 1.63 0.01 1.657 0.012 1.632 0.019 1.658 0.065 1.632 0.030 1.658 0.055 1.632 0.057 1.658 0.172 1.632 0.009 Sillimanite...... 1.660 0.021 Bityite...... 1.63 Strong. 1.660 0.012 1.63 0.022 Tilasitc...... 1.660 0.035 1.63 0.02 1.660 0.012 1.63 0.05 1.66 0.06 1.63 0.013 1.66 0.015 1.632 0.036 1.660 0.021 1.633 0.006 Triplite...... 1.660 0.022 1.633 0.004 1.660 1. 634 - 0. 004 1.661 0.043 Melilite...... 1.634 0.005 Erythrite...... 1.661 0.073 Apatite...... 1.634 0.003 1.661 0.040 Podolite...... 1.635 0.007 1.662 0.017 Pitticite...... J.635-)- 0.000 1.662 0.013 Pahliite...... 1. 635 0.004 1.662 0.098 Gedrite...... 1.636 0.021 Friedelite 1.664 0.035 Grandidierite...... 1.636 0.037 1.665 0.02 ± 1.636 0.035 Triplite...... 1. 665± 0.02 1.636 0.029 1.666 0.016 Barite...... 1.637 0.012 1.666 0.012 Cumingtonite...... 1.638 0.022 1.666 0.005 1.638 0.052 1.667 0.011 Glaucophane ...... 1.638 0.017 1.667 0.147 Andalusite...... 1.638 0.011 1.667 0. 027 1.64 ± 0.01 1.668 0.068 1.64 1.668 0.016 1.64 0.02 1 fifiQ 0.012 Svanbergite...... 1.64 0.01 1.669 0.009 Griphite...... 1.64 ± 0.000 1.669 0.011 1.64 ± 0.000 0.031 Homilite (altered) ..... 1. 640± 0.000 1.669 0.012 1.642 0.000 1.67 ± 0.000 1.642 0.024 1.670 0.04 1.642 0.063 1.67 0.014 1.642 0.015 Hibschite...... 1.67 0.000 Hornblende...... 1.642 0.024 1.670 0.032 Margarite...... 1.643 0.013 1.670 0.01 1.643 0.035 1.670 Weak. 1.643 0.020 1.671 0.029 Plancheite...... 1.644 0.058 1.67 0.02 1.644 0.053 1.671 0.146 Fairfieldite...... 1.644 0.018 1.671 0.019 1.645 0.03 1.671 0.030 Elbaite...... 1.647 0.018 1.672 0.004 (?)' 0.01 1.673 0.048 1.649 0.006 1.673 0.022 1 649 0.075 1.674 0.039 1.649 0.012 1.674 0.013 1.65 0.025 1.674 0.036 1.65 ± 0.011 1.674 0.019 1.65 ± 0.000 1.675 0.028 1.65 0.01 1.675 0.044 0.026 1.675 0.039 1.65 0.06 1.675 0.085 1.650 0.02 1.676 0.000± Barrandite...... 1.65 + 0.03 Parisite...... 1.676± 0.081 TABLES FOR DETERMINATION OF MINERALS. 167

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, fi, and showing their birefringences Continued.

0 Birefringence. 0 Birefringence.

Witherite...... 1.676 0.148 Strengite (manganif- 1.676 0.012 1.714 0.025 1.678 0.041 Brandtite...... 1.715 0.013 1.678 0.033 Woehlerite...... 1.716 0.026 1.679 0.011 1.716 0.190 1.68 ± 0.000 1.716 0.005 1. 680± 0.005 1.717 1.101 1.68 0.005 Clinozoisite...... 1.719 0.007 1.680 0.029 1.72 ± 0.000 1.680 0.037 Trimcrite...... 1.720 0.010 Strong. 1.720 0.016 1.68 0.05 1.720 0.029 1.681 0.016 Adelite...... 1.721 0.019 1.68 0.18 1.721 0.095 1.682 0.155 Glaucochroite ...... 1.722 0.049 1.683 0.055 Diaspore...... 1.722 0.048 1.684 0.161 Spinel (pure)...... 1.723 0.000 Axinite...... 1.685 0.010 Pyrochroite...... 1.723 0.042 Schroeckingeritc...... 1.685 0.032 1.724 0.022 1. 685. 0.094 Basaltic hornblende .... 1.725 0.072 1.685 0.012 Sarcopside...... 1.725 Weak. 1.685 0.014 Homilite ...... 1.725 0.023 1.68 0.03 Rowlandite...... 1.725 0.000 1.685 0.033 Babingtonite ...... 1.726 0.033 'Pri oil o 1 r»i f~ p 1.686 0.028 Triploldite...... 1.726 0.005 1.686 0. Oil Magnesito (FeC03, 15 1.687 0.046 percent)...... 1.726 0. 1*99 1.687 0.029 Tyrolite...... 1.726 0.036 1.687 0.005 Berzoliite...... 1.727 0.000 1.687 0. 029 Picrotephroite 1.688 0.031 (Mg2Si04, 40.4 per 0.004 cent; Mn2SiC>4,59.6).. 1.727 0.029 Triphvlite...... 1.688 Ganophyllite ...... 1.729 0.025 Zippeitc...... 1.689 0.109 Clinozoisite...... 1.729 0.010 Thorite (altered)...... 1.69 0.000 Mixite...... 1.730 .0.080 1.690 0.028 Melanocerite...... 1.73 ± 0.01 Stilpnomelane...... 1.69 ± 0.09 Piedmontite...... 1.73 0.02 Hastingsite...... 1.69 Weak. Ottrclite...... 1.73 0.01 Ehodizite...... 1.69 0.00 ± Augite (TiOs, 4.84 per Oehlenite...... 1.691 O.OOOi cent)...... 1.73 0.021 1.691 0.021 Rhodonite...... 1.73 0.011 Pharmacosiderlte...... 1.693 0.005 1.73 0.056 Willemite...... 1.694 0.029 1.730 0.068 Kaersutite...... 1.694 0.032 Stibiconite (?)...... 1.73 0.01 ± Spangolite...... 1.694 0.053 1.731 0.028 Riebeckite...... 1.695 Low? 1.731 0.022 Basaltic h ornblen do .... 1.695 0.031 1.732 0.032 Hiortdahlite...... 1.695 0.012 Molybdite...... 1. 733± 0.215 Gruenerite...... 1.697 0.045 1.733 0.050 Euchroite...... 1.698 O.C38 1.733 0.019 Ankeritc (CaC03, 52.6 1.734 0.033 percent; MgC08,36.7; 1.698 ' 1.735 0. 035 FeCOs, 10.7)...... 0.185 Sicklerite...... 1.735 0.030 Neptunite ...... 1.699 0.046 Roselite...... 1.735 0.01 Stibiconite...... 1.70 ± 0.000 1.736 0.000 1.70 0.000 Grossularite (pure) ..... 1.736 0.000 1.736 0.110 Magnesito (pure)...... 1.700 0.191 1.737 0.019 Crocidolite...... 1.70 0.025 1.737 0.055 Gadolinitc...... 1.70 0.05 1.737 0.000 Johannite (?)...... 1.70 Moderate. 1.738 0.013 1.70 Low. 1.739 0.024 Planchcite...... 1.70 0.04 Helvito 1. 739 0.000 1.70 0.021 Pilbarite...... 1.74 ± 0.000 Triphylite...... 1.702 Mod. Caryoceritc (altered).. . . 1.74 ± 0.000 1.702 0.013 1.74 0.035 Zoisite...... 1.702 0. 006 / Rather 1. 703 0.005 VilD-tcito 1 74 \ strong. Astrophyllite...... 1.703 0.055 1.74 dk (?) 1. 704 0.025 1.74 0. 089 1.705 0.000 1.74 0.05 Tarbuttite...... 1.705 0.053 1.741 0.010 Graftonitc...... 1. 705 0.024 'Pvrmv 1.742 0.000 Svabite...... 1.706 0.008 1. 742 0.027 BarkoviMte ...... 1.707 0.021 1.745 0.003 1.708 0.003 Mixito...... 1.745 0.085 1.709 0.006 1.745 0 087 1.71 0.035 1.748 0.010 1.710 0. 000 1.749 0.202 Zippeito (?)...... 1.710 0.100 1.750 0.03 1.711 0. 010 Rutherfordine ...... 1.75 0.08 Gerhardtitc...... 1.713 0.019 Molybdite...... 1.75 ± 0.21 168 MICROSCOPIC DETERMINATION .OF NONOPAQTJE MINERALS.

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, £, and showing their birefringences Continued.

0 Birefringence. ft Birefringence.

1.75 1 Low. Leucochalcite...... 1.817 0. 032 Chloritoid...... 1.75 ± 0.01 ± 1.818 0.000 1.75 0.045 Cerite...... 1.818 0.400 Spinel...... 1.75 ± 0.000 Smithsonite ...... 1.818 0. 200 3D&vicsit6 1.752 0.016 Cornwallite...... 1.82 0.04 1.754 0.039 1.82 0.09 1.754 0.021 (?) Strong. 1.754 . 0.000 Erinite...... 1.825 0.06 VGK&sitc 1.755 0.065 Ehodochrosite...... 1.826 0.221 Tritomite (altered) ..... 1.757± 0.000 1.826 0.000 1.757 0.047 1.83 O.OOOi 1 758 0.108 1.830 0.000 Yttrialite...... 1.758 0.000 1.83 0.000 1.70 0.13 Siderite(MgC08,24 per 1.760 0.183 cent) ...... 1.830 0.234 1. 760 0.000 Higgensite ...... 1.831 0.046 1.760 0.090 Knebelite ...... 1.831 0.047 f Rather Natrojarosite ...... 1.832 0.082 (?) strong. Chalcosiderite ...... 1.834 0. 072 1.762 1.086 Uvarovite ...... 1.838 0.000 1.763 0.000 1.838 0.050 1.768 0.008 Tagilite...... 1.84 0.16 Strong, 1.84 Strong. B, ± 0.000 1.840 0.055 Aegirite (vanadiferous) . 1.770 0.037 1.840 0.096 1.771 0.031 1.842 0.032 1.771 0.061 Siderite(MnCO3, lOper 1.77 0.000 cent)...... 1.849 0.234 Melanocerite (altered). . 1.77 ± 0.000 (fi Weak. 1.773 0.078 1.85 0.17 1.774 0.032 Magnesioludwigite ..... 1.85 0.15 Barthite...... 1.774 0.013 1.85 0.04 (?) Strong. Toernebohinite ...... 1.852 0.033 1.774 0.06 1.853 ' 0.050 1.776 0.037 Siderite...... 1.855 0.242 1. 778± 0.000 Sphaerocobaltite...... 1.855 0.25 1.778 0.023 1.857 0.000 1.778 0.073 1.86 0.07 1.779 0.019 Bindheimite...... 1.86 ± 0.000 Thortveitite...... 1.78 0.046 1.861 0.049 1.78 0.13 Fayalite...... 1.864 0.050 1.780 0.029 1. 865± 0.04 ± 1.78 ± 0.005 Caledonite...... 1.866 0.091 Shattuckite...... 1.782 0.063 1.87 db O.OOOi 1.786 0.046 Chalcolamprite ...... 1.87 db 0.000 1.786 0.040 Arseniosiderite ...... 1.870 0.078 Mesitite 1.788 0.218 Synadelphite ...... 1.87 0.04 1.788 0.082 Clinoclasite...... 1.870 0.18 1.788 0.027 1.870± 0.225 1.788 0.023 Siderite (pure)...... 1.875 0.242 1.788 0.051 Plumboiarosite ...... 1.875 0.089 1.79 0.10 1.875 . 0. 254 Molybdite...... 1.79 ± 0.26 ± 1.879 0.240 1.79 0.020 Hemaflbrite ...... 1.88 0.06 1.792 0.035 Tscheffkinite...... 1.88 ± 0.01 1.792 0.034 1.88 0.08 Sarkinite...... 1.793 0.022 f Rather 1.793 0.028 1.88 1 strong. 1.794 0.009 1.882 0.017 Barthite...... 1.795 0.035 Catoptrite ...... (?) 0.000 1.799 0.050 Heterosite...... 1.89 0.05 1.80 Strong. 1.895 0.000 (?) (?) Carnotite...... 1.895 0.20 1.800 0.000 1.898 0.083 FlinMte...... 1.801 0.050 1.90 0.22 1.80 0.006 Stibiconite...... 1.9 ± 0.000 1.8 0.015 1.9 ± 0.015 1.80 0.08. 1.907 0.134 1.80 0.25 1.91 0.01 ± ninnlroritA 1.80 0.05 1.91 Strong. 1.80 ± 0.000 1.91 0.035 1.80 ± 0.000 1.913 0.010 1.80 ± 0.000 Hugelite...... 1.915 0.01 1.801 0.000 Scheelite...-...... 1.918 0.016 1.810 0.091 Claudetite...... 1.92 0.14 1.810 0.022 1.920 0.071 1.81 0.042 1.92 ± 0.04 ± 1.811 0.000 1.92 ± 0.000 Beckelite 1.812 0.000 1.923± 0.045 1.81-5 0.054 Microlite..--...... 1.925 0.000 1.815 0.050 1.925 0.200 1.817 0.105 CorMte...... 1.93 Weak. Phndnp.hrnsit,fi fnnr«V_ 1.817 0.22 Tvuvamunite ...... 1.93 ± 0.20 TABLES FOE DETE'RMIK'ATIOnsr OF MIETEBALS.

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, 0, and showing their birefringences Continued.

ft Birefringence. ft Birefringence1.

1 QQ 0. 000 2.15 Strong. 1.935 0.115 Goethite (impure) ...... 2.15 ± 0.07 1.94 0.000 Atelestite...... 2.15 0.04 1 04 -1- 0.000 Bismutite...... 2.16 ± 0.05 ± 1.945 0.026 Chromite ...... 2.16 ± 0.000 1 Q<\ 0.04 Bellite...... 2.16 0.02 1 Tellurite...... :.. 2. 18 Li 0.35 1.967 0.011 2.182 0.01 TcMinfFlrirutA fallfcrArl?\ 1.97 0.02 Zirkelite...... 2.19 0.000 1.97 0.04 Kleinite (hexagonal) .... 2.19 0.02 1 07^ 0.683 2.19 0.07 1.975 0.134 2.195± 0.000 1.98 0.000 2. 195± 0.000 1 OR 0.000 2.20 0.000 1.985 0.10 0.000 1.99 0.09 2.20 0.000 Asricolitc 1.99 Very low. 2.20 ± 0.000 1 OQ -i- 0.000 2.20 ± 0.000 1 007 0.096 2.20 0.000 Bindheimite (?)...... - 2.0 Strong. Kentrolite...... 2.20 0.21 Wiikite...... 2.00 0.000 Tripuhyite...... 2.20 0.14 2.0 ± 0.015 2.200 0.57 2.00 0.000 Phoenicochroite...... (?) (?) Leadhillito...... 2.00 0.14 2.205 0.000 Samarskite...... 2.21 ± 0.000 lodyrite. .:...... 2.21 0.01 2.00 0.15 Polymignite...... 2.215 0.000 Zincite...... 2.008 0.021 2.217 0.060 2.01 ± 0.000 Huebnerite...... 2.22 0.15 Volborthite...... 2.01 0.02 Vauquelinite ...... 2.22 0.11 2.01 0.19 Goethite...... 2.22 0.08 2.026 0.061 2.24 ± 0.000 f Rather 2. 24 Li 0.29 2.03 Manganite...... Voltzite...... ft* 4i^ 0.17 2.03 0.03 2.25 0.05 9 ndQ 0.290 2.25 ± 0.000 2.05 0.000 2.253 0.000 2.05 ± 0.000 2.25 0.07 2.05 ± 0.000 Tantalite...... 2.25 0.15 2.05 0.02 2.26 0.17 2.05 Strong. Cuprodescloizite...... 2.26 0.15 2.05 Very low. 2.26 0.16 2.050 O.OOS 2.26 ± 0.00 2.05 0.09 2.26 ± 0.05 2.05 0.157 Stolzite...... 2.269 0.087 Sipylite...... 2.06 ± 0.000 Tapiolite...... 2.27 ti 0.15 2.06 ± 0.000 2.' 27 0.03 2.06 ± 0.000 Mendipite...... 2.27 0.07 2.061 0.000 2.27 0.17 2.065 0.000 (?) (?) 2.07 0.000 Goethite...... 2.29 0.14 2.07 0.02 2.29 0.08 2.076 0.274 (?) 0.000 2.087 O.OOOi 2.30 0.000 2 no 0.000± 2.30 0.000 2.09 0.15 Hielmite...... 2. 30 u 0.10 9 no -i. 0.15 Plattnerite.... '...... 2.3u± (?) 2 no 4- 0.01 2.31 t, 0,12 (?) (?) Geiklelite...... 2.31 0.36 2 1 0.08 2.32 0.17 2.10 0.53 2.32!.! 0.07 Fiedleritc...... 2.102 0.310 Wolframite...... 2.32 ti 0.16 2.114 0. 026 (?) 1?) 2. 115± 0.000 2.33 Weak. 2.116 0.081 2.34 ± 0.20 2.12 0.000 2.346 0.000 2 10 i 0.000 Goethite...... 2.35 L 0.14 2.13 0.08 Schwartzembergite .... 2.35 0.11 2.13 0.19 Valentinite...... 2.35 0.17 2.135 0.017 2.35r, 0.000 2.142 0.000 2.35 L 0.10 2 11 0.000 2. 35 i. 0.02 2.15 ± 0.000 Vanadinite...... 2.354 0.055 Embolite...... 2.15 ± 0.000 Wurtzite...... f 2.33,. 0.02 Matlocklte...... 2.15 0.11 , \j£f*t 170 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

TABLE 6. List of minerals arranged according to their intermediate indices of refraction, /3, and showing their birefringences Continued.

P Birefringence. /3 Birefringence.

2. 36 Li ± 0.000 2. 61 Li 0.20 2. 36 Li 0.11 Rutile...... 2.616 0.287 2. 36 Li 0.05 Arizonite ...... 2. 62 Li Moderate. 2. 36 Li 0.15 Tenorite...... 2. 63red Strong. Brackebuschlte...... 2. 36 Li 0.20 / 2. 633Li 0.040 / 2. 34 Li 0.00 \ 2.654Na 0.043 Sphalerite (pure) ...... \ 2.37 Na 0.00 2. 64 Li 0.32 2. 37 Li 0.35 2. 665Li 0.130 2.38 Weak. 2. 69 Li 0.000 2. 39 Li 0.04 2. 70 Li 0.000 Ferberite ...... 2. 40 Li Strong. / 2.819Li 0.327 Ferrocolumbite...... 2. 40 Li Extreme. \ 2.857Na 0.347 2. 402Li 0.098 Cuprite...... 2.849 0.000 2.404 0.083 2.979Li 0.268 2.419 0.061 3. 2.419 0.000 3. 2. 42 Li Weak. Polybasite...... 3. f 2.43lLi 0.025 Hematite...... 3. 01 Li 0.3 I 2.506Na 0.023 3.084 0.203 2. 45 Li Hutchinsonite ...... 3.176Na 0.110 2. 45 Li 0.06 Hematite...... 3. 22 Li 0.28 2. 46 Li 0.31 Smithlte...... 3.27? Stibnite...... 4.303 1.109 2. 47 Na 0.000 >2. 72 Li 0.000 2.481 0.271 >2. 72 Li O nnn 2. 49 Li 0.000 Chalcophanite ...... >2. 72 Li 2. 50 Li >2. 72 LI 2. 50 Li >2. 72 Li 2.5 L! 0.28 *-*9 79 2. 50 Li 0.10 >2.72 Li fTiir(rit'fi 2. 55 LI 0.10 Dufrenoysite ...... >2. 72 Li Koechlinite...... 2. 55 LI >2. 72 LI 2.554 0.061 (?) Smithlte...... 2. 58 Li 0.12 (?) 2.586 0.158 . (?) 2. 59 Li 0.15 Vrbaite...... (?) 2.6 Li Extreme.

Abbreviations used in Table 7. abs...... absorption. isomor...... isomorphous. acic...... acicular. isot...... isotropic. amor...... amorphous. mic...... micaceous. anom...... anomalous. mkd...... marked. B...... birefringence. mod...... moderate. b. b...... before the blowpipe. mon...... monoclinic. biax...... biaxial. oct...... octahedral. cleav...... cleavage. opt...... optical. conct...... concentrated. orient...... orientation. conch...... conchoidal. orth...... orthorhombic. decpd...... decomposed. penet...... penetration. dif...... difficult. perf...... perfect. disp...... dispersion. perc...... perceptible. dist...... distinct. pi...... plane. dodec...... dodecahedral. pleoc...... pleochroism; pleochroic. elong...... elongation. poly...... polysynthetic. ext...... extinction. pris...... prismatic. extr...... extreme. ps...... pseudq. F...... fusibility. pyram...... pyramidal.. fib...... fibers; fibrous. rect...... rectangular.. fus...... fusible. rhomboh...... rhombohedral. G...... specific gravity. sol...... soluble. gelat...... gelatinous; gelatinize. sq...... square. H...... hardness. tab...... tabular. hex...... hexagonal. tetrag...... tetragonal. imperf...... imperfect. tetrah...... tetrahedrons. incl...... inclined. tr...... trace. indist...... indistinct. trie...... triclinic. infus...... infusible. trig...... trigonal. insol...... insoluble. tw...... twinning. isomet...... isometric. uniax...... uniaxial. TABLE 7. Data for the determination of the nonopaque minerals.

Isotropic group. [Most of the. minerals of this group are isometric: a considerable number are amorphous and therefore rather variable and indefinite in their chemical composition and all their properties; a few, which are included also in the proper birefracting group, are birefracting, but their birefringence is so weak or uncertain as to make them easily mistaken for isotropic minerals.]

Crj'stal system and Hardness and 77. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks.

G=2.75 Sol. in hot H2O. 2KF.SiF4 oct. 1.32S {001>perf. {100}.. H=3.5 Sol. in H2O. Very weak B. Uniax. . «=car- g NaF met. Massive. {010}dist. G=2.79 mine red, «= golden yellow. 1 T*? \Vofor Fluid ...... G=1.00 H2O 1 339 <110}dist...... do...... H= 2.5 to 3 Sol. in acids. F=easy. 3NaF.3LiF.2AlF3 G=2.78 G=2.0 2NH4F.SiF4(?) oct. Claylike...... White, etc...... H=2 Slowly sol. in HOI. F=dif. Anom. B due to ten­ AlsO3.6SiO2.18±HsO(?) sion. 1.406± H=G± Insol. in acid; sol. in KOH. SiO2.«HaO G= 1.9 to 2.3 Oct...... H=4.5 Decpd. by HaSO^. Infus. Opt. anom. Divides (Na2,Mg)F2.3Al(F,OH)s.2H2O yellowish. G=2.6i into birefracting octahedral segments. 1 434 {lll>perf...... H= 4 to 5 Sol. in acid. Infus. (Y,Er,Ce)F3.5CaF2.H2O G=3.36to3.63 1 434 .... .do ...... do...... H=4 Sol. in acids. F=1.5. CaF2 etc. G=3.18 1 440± H=6± Sol. in KOH; insol. in acid. Infus. SiO3.wH2O G=2.1± 1 454 H=3.5 Slowly sol. in H2O. F=l. 2NaaO.2SO3.NaCl.NaF G=2.49 Oct ...... do...... do...... H=2 Potash alum. Sol. in HaO. F=l. KaO.Al2O3.4SO3.24HsO G=1.76 TABLE 7. Data for the determination of the nonopaque minerals Continued. Isotropic group Continued. to B Crystal system and Hardness and I I n. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks. o cw 1. 457 ± {lll>imperf...... H=4.5 o (Ca3,Y2)F6 G=3.55 o 1.459 Oct...... White...... H=2 Alum group. Sol. inH2O. F=l. Opt. anom. o (NH<)2O.A12O3.4SO3.24H2O G=1.64 1.46 H-6± SiOa.nH^O G=2.2± 1.461 Melanophlogite...... Cubes...... Colorless ...... H= 6.5 to 7 Insol. in acid. Infus. Contains SiO2, SO3, and H2O G=2.04 1.47± H=4 Decpd. by acid. F=dif. MnO.SiO3.nH2O G=2.6 1. 470± .....do...... H-2 Al2O3.2SiO2.nH2O opaline. G= 2.0 to 2.2 with 25 per cent H2O. On long exposure to dry air or on heating to 60° C. for a few hours n in­ creases to 1.555. 1.47± H=3 Al2O3.SiO2.nH2O G=1.8± 1.48 Oct...... {lll>dist...... White...... H-5 Zeolite group. Decpd. by acid. F=3. Uniax. + N a2O .CaO .2Al2O3.10SiO2.20H2O O=l. 92 in eight segments from loss of H2O. 1.483 {110>poor...'...... H=6 Sodalite group. Gelat. F=3.5 to 4.0. 3Na2O.3Al2O3.6SiO2.2NaCl G=2.2± 1. 48,5 H=4 Sol. only in hot H2RO4. Infus. 3Al2O3.P2Oi.l8±H2O tioiis. 0=1.94 1.486 White...... H-6to7 SiO2 G=2.3 1.487 <211>...... poor...... H=6 Sodalite group. Gelat. F=4.5. 5NajO.3Al2O3.6SiO2.2SO3 G=2.3± 1.496 .....do...... do...... do...... H=6 Do. ~ 5(Na2,Ca)O.3Al2O3.6SiO2.2SO3 G=2.4 1.50± .....do...... do...... Azure blue...... H=6 Sodalite group. Gelat. F=3.5. Anom. disp. 3NaaO.3Al2O3.6SiOa.2Na2S G=2.4 7u.i=1.63, 71(520 w)= 1.51, 71(450 W)= 1.535. 1.5 Yellow...... 0=2.2 Near evansite. Easily sol. in HNO3. Infus. but Hydrous phosphate of Al, Pb, stalactitic. blackens b. b. and Cu. 1.508 Tychite Oct...... H=3.5 Compare with northupite. Almost insol. in H2O; 2MgO.3NasO.4C6V.SOs G= 2.46 to 2.59 sol. in acids. F«=l. 1.50± .....do...... 3MgO.4SiO2.7iH2O 1.509 Decpd. by acid. Infus. Birefracting below 500° C KsO.Al2O3.4SiO2 G=2.47 Twin lamellae. Symmetrical inclusions. 1.514 Northupite...... Oct...... None...... do...... H=4 Slightly sol. in H2O; sol. in acid. F=l. Tw. com­ MgO.Na2O.2CO2.NaCl G=2.38 mon. 1.51± Black or brownish H=3 Decpd. by acids. Infus. Opal-like. In part finely FejjO3,MgO,FeO,SiO2,H2O,etc. black. G=2.5to3 crystalline. 1.517 .....do...... H= 1.5 to 5 Slightly sol. in acid. B. b. decrepitates. In part 3Ala03.2P2O5.18±H20 G=2.65 birefracting. 1.517 .....do...... do...... White...... Soft Amorphous part of sepiolite. 2MgO.3SiO2.7iH2O(?) 1.52± Halloysite...... Amor., earthy...... do...... White, yellow. .... H=lto2 Insol. in acid. Infus. On drying at about 60° C. Al2O3.2SiO2+nH2O G= 2.0 to 2.2 n increases to 1.555. 1.52 Cubes...... Soft Very deliquescent. F=1.5. CaCla G=2.2 1.525 ....do...... H=6.5 Related to leucite. Decpd. by acid. F=dif. 2CssO.2Al2O3.9SiO2.H2O G=2.90 co TABLE 7. Data for the determination of the nonopaque minerals Continued. Isotropic group Continued.

Crystal system and Hardness and n. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks.

1 53± Reddish...... H-2.5 Gelat. F-4(?). 5MgO.6SiO2.4±H2O I CQi White...... G-2.34 3(Zn,Ca)O.2Al2O3.P2O5. 27±H2O 1.535± Soft Hydrocarbon. vitreous luster. G=1.07 1.54± .....do...... do...... H-4 Decpd. by acid. F=dif. MnO.SiO2.wH3O G=2.7

1 W^i H-3to4 Sol. in H2O. Absorbs H2O in air. F=2. K2O.2MgO.3SO3 tetrah. G=2.83 1.54± Cornuite ...... Amor...... None...... Bluish green ...... mCuO.nSiO2.H2O 1.542± .....do...... White...... H-2 Al2O3.2SiO2.nH2O G=2.6 n increases to 1.555. 1.544 H-2.5 Sol. inH2O. F=1.5. NaCl G=2.17 1.548± White...... Soft Al2O3.4SiO 2.6H2O(?) G=1.73 1.555 .....do...... H-2 Al203.2Si02.2H20 G=2.6

MnCU 1.569 .....do...... H-2 to 2.5 Sol. in acid. F=5(?). CaO,P2O5,H2O,CO2, etc. G= 2.7 to 2.8 1.57± .....do...... H=3 Banded, n varies from 1.56 to 1.61. 3NiO.CO2.7iH2O(?) G=2.6 1.571 Nitrobarite...... G-3.25(?) Sol. inH2O. F=l. BaO.N2O5 1.584 White...... H= 3 to 3.5 Uncertain clay mineral. 8Al2O3.3SiO2.30± HjO G=1.95to2;05 1.589 Tetrah...... <111}...... H=7 Insol. in acid. Infus. 8A l2Os.6SiO2.9H2(O,F8,Cl!) G=2.88 1.59± H=3 Decpd. by acid. Infus. Opal-like. In part FesOsjMgO^eO.SiOjjHsO.etc. black. G=3 finely crystalline. 1.59± .....do...... do...... Emerald-green .... H=3 n varies from 1.56 to 1.61. 3NiO.CO2+wH2O(V) G=2.6± 1.59± .....do...... H=2 Easily sol. in acid. F=5(?) CaO,P2O5,CO2) H2O, etc. G=2.7± 1.59 H=2± A serpentine. Decpd. by HC1. Infus. (Ni,Mg)O.SiO2 .wH20 G=2.6± 1.60± H=4to5 Insol. inacid. Infus. TO highly variable. (Seep. 136.) Sb2O4.nH2O(?) orless. G=o± 1.60± .....do...... do...... Reddish brown. . . H=3.5 Sol. in acid. F= 3 to 4. n varies from 1.57 to 1.67. 3CaO.7FesO3.2P205.24±H2O(?) G=2.7± 1.602 Voltaite...... Dull oil-green, H=3 to 4 Partly sol. in H2O; sol. in acid. In section oil-green. 5(Mg.Fe,K3)0.2(Al,Fe)203. brown, black. G=2.79 10SO8.15n2O 1.61± H=3 n varies from 1.56 to 1.61. 3NiO.COs .wH2O(?) G=2.G± 1.61± Diadochite...... do...... Brown, yellow. . . . H=3 Sol. in HC1. F=easy. 2Fe2O0.P2O6.2SO3.2H3O G=2.03± 1.61± .....do...... White...... H=2 Sol.inHCl. F=5(?). CaO,P2O5,H2O,CO2) etc. G=2.9± 1.61± OiiTTiTnif-.p...... do...... H=2.5 Sol. in acid. Infus. Greasy. Alteration of ura- (Pb,Ca,Ba)O.3UO3.SiO2.5H8O G=4.0± ninite. May bo crystalline. 1.635± Pitticite...... do...... H=2.3 Sol. in HC1. F=easy. FeaOsjSOajAsssOsjHaO, etc. white. G=2.3 1.64± Brown...... H=5.5 Do. MnO,P2O6,H2O, with Fe,Al, G=3.4 Ca, etc. 1.64± Lagonite...... Amor., earthy..... Ocber-yellow...... Soft FesO3.3B2Os.3H2O 1.640 Black...... H=5 -a 3(Ca,Fe)O.Bs03.2Si02.nH20(?) G=3.35 Cn TABLE 7 .- Data for the determination of the nonopaque minerals Continued. Isotropic group Continued. Oi

Crystal system and Hardness and n. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks. o

CO 1.642 H= 1.5 to 2 Sol.inH2O. F-l. Volatile. o NH4C1 G=1.53 o 1.65± H=3.5 Sol. in strong acid. F=3. Fe2O8.P2O5.6±H2O G=2to3 1.65 H= fragile Sol. in acid. F=l. 6Fe2Os.CaO.54P2O5.23± H2O G=2.66 1.67± .....do...... H=3.5 Sol. in acid. F=3 to 4. n varies from 1.57 to 1.07. 3CaO.7Fe2Os.2P2Os.24± H2O G=2.7± 1.67 Onf H=6 Sol. in acid. Infus. Some crystals B and divided CaO.Al2O3.2SiO2.2H2O G=3.05 into sectors. 1.676 H=2.5 Sol. inHCl. F=l. Anom..B. 3Fe2O3.2As2O5.3(H,K)2O.5H2O G=3.0 1.68± H=6 Epidote group. Alters to a brown, birefracting 4(Ca.Fe)O.3(A],Ce,Fe,Di)2O3. G=3.5to4.2 rorm. May gelat. F=3. 6SiO2.H2O 1.69 H=8 Insol. in acid. Infus. Opt. anom. (K,Cs,Rb)a0.2Al2O3.3B203 G=3.40 1.69 Thorite (altered)...... -{110 Mist...... Black, b r own, H=4.5too Gelat. Infus. Isot. from alteration or inversion. Th02.Si02.«H2O pyramids. green, orange. G= 5.2 to 5.4 eO 1.7± H=4to5 Insol. in acid. Infus. n highly variable. Cj Sb2O4.7iH2O(?) G=5.00 1.70 Ps. orth. Thin .....do...... Dark brown to H=5to6 Blomstrandine group. Decpd. by HjSOi. Infus. Columbate and titanate of Y, pris. c. Tab.<010} black. G=5.00 U,Th,Fe,etc. 1.705 JPvroDG Red...... H-7...... 3MgO.Al2d3.3Si62 {110><2ll}etc. G= 3.510 acid. F=3£. 1.710 Rhombic clodce...... do...... Colorless...... H=6.5 3CaO.Al2O3.(SiO2,CO2).2H2O G=3.13 1.72± Ps. mon.(?)...... Imperf...... Brown, black ..... H=6 Epidote group. Alters to a brown, birefracting 4(Ca.Fe)O.3(Al,Ce,Fe,Di)jO3. G=3.5to4.2 form. Maygelat. F=3. eSiOj.HjO 1 723± Oct...... Red, etc...... H=8 Spinel group. Insol. in acid. Infus. Tw. after MgO.AljOj G=3.6± {111}, n is for the pure artificial mineral. 1.725 Conch...... Drab-green to red . H=6to7 Near gadolinite. Gelat. Infus. Pale green in 2Y2O3.3SiO G=4.52 splinters. 1.727 None...... Sulphur - yellow H=5 Sol. in acid. F=3. 3(Ca,Mg,Mn)O.AssO5 to orange-yellow. G=4.05

1 7QC Isomet. , .....do...... Varies...... H=6 Garnet group. Insol. in acid. F=3. Opt. anom. 3CaO.Al2O3.3SiO8 {211}, etc. 0=3.530 Data for pure mineral. 1.736 {100} perf., {111} Colorless...... H=5 Sol. in add. Infus. MgO oct. poor. G=3.6 1.737 Red to gray...... H=6 . Nearhelvite. Gelat. F=3. 3(Fe,Zn,Mn)O.3GlO.3SiOj. G=3.43 (Fe,Zn)S 1 73Q {111} tr...... Yellow, etc...... H=6 Gelat. F=3. 3(Mn,Fe)O.3GlO.3SiO2.MnS G=3.2 1.74± PUbarite...... H=3 Sol. in acid. UO2.ThO2.PbO.2SiO2.4H!O G=4.6± 1.74± Ps. trig. Tab. Conch...... Nut-brown...... H=5 to 6 Near melanocerite. Sol. in hot HC1 with separa­ Silicate of Y,Ce.Ca,etc., con­ rhombs. G=4.30 tion of SiOj. B. b. swells without fusing. Iso- taining F and B. tropic through alteration. 1 749 "PufnTifl Red...... H=7 Garnet group. Insol. in acid. F=3.5. Data for 3(Mg,Fe)O.AlsO3.3SiO2 {211}, etc. G=3.715 mineral with percentages of CrjOs= 2.4,FeO= 10.2. MgO=18.4, CaO=4.5,MnO=0.5. 1.75± Spinel...... Isomet. { 1 1 1 >, Black, -green in H=7.5 Spinel group. Insol. in acid. Infus. (Mg,Fe)O.AlsO3 rarely {100}. section. G=3.75± 1.755 White...... H=1.5 Sol. inH2O. F=l. Volatile. AssO3 G=3.70 1. 757± T>o trirr H=5.5 Gelat. Silicate of Th, Ce, Y, Ca, etc., G=4.2 containing F and B. 1 7WJ Yttrialite...... Black,brown,olive H=5to7 Sol. in HCI. Infus. Pale green in section. (Y,Th)sO3.2SiO 8 green. G=4.58 1.760 Isomet.{110>,{2Hh None...... Dark red, etc..... H=7 Garnet between pyrope and almandite. Insol. in 3(Mg,Fe)O.Al2Os.3SiO2 etc. G= 3.837 acid. Infus. Data for mineral with percentages of Fe,Os=1.9, FeO= 15.6, CaO= 0.9, MgO=17.2. TABLE 7. Data for the determination of the nonopaque minerals Continued. Isotropic group Continued. GO

Crystal system and Hardness and n. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks.

1.763 Isomet. {110}, None H-6 3CaO.(Al,Fe)4Os.3SiO2 t211>, etc. G=3.633 F=3. Data for mineral .with percentages of Fe203=7.2,MnO=0.1. L77± Melanocerite (altered) ...... Ps. trig. Tab. H==5 to 6 Ce,Y,Ca,B,Fe,Si,etc. <0001>. black. G=4.13 1.77 Macktutoshite...... Black...... H-5.5 Silicate of U, Th, Ce, etc. , con­ prisms.' G=5.44 colorless but clouded. taining HZO. 1.77± Pleonaste ...... Isomet. <111>, .....do...... H-7.5 (Mg,Fe)O.Al808 rarely {100}. G=3.8± in section. 1.778 Almandite...... H-7 3FeO.AlaOs.3SiO 2 {211>, etc. G=4.04 mineral with percentages of Fe2O3=3.3. MnO= 1. 2. CaO=2.5, MgO=3.1. 1.780± Gadolinite ...... H- 6.5 to 7 2GlO.FeO.YsO3.2SiOs black. G= 4.0 to 4.5 and n increases to 1.820. 1.80± Hercynite...... H-7.5 FeO.AlsOs G=3.9 in section. 1.800 Spessartite ...... Isomet. { 1 1 0 } , H-7 3MnO.AIsO3.3SiOs {2ll>, etc. G= 4.180 acid. F=3. 1.80± H-7.5 to 8 ZnO.Al*O3 0=4.55 1.8± Stibiconite ...... H-4to5 SbsO4.nHsO(?) G=5± 1.801 Isomet. { 1 1 0 > , H-7 3FeO.AlaO3.3SiOs {2ll>, etc. G= 4.093 mineral with percentages of MnO= 1.5. CaO=2.0, MgO=5.3. 1.811 .....do...... H-7 3(Mn,Fe)O.AhO3.3SiO2 G= 4.273 mineral with percentages of FeO= 11.1 .MnO= 32.2. CaO=0.6, MgO=0.2. 1.812 <100>dist...... Light yellow, H=5 Sol.inHCl. Infus. Large crystals areanisotropic. 3CaO.2(Ce, La, Di)sO3.3SiO2 Oct. brown. G=4.14 In section yellow. 1.818 Conch...... Dark green or H=7.5 Probably related to zircon or malacon. ZrO3,SiO2, with UO3,ThO2, gates. Dodeca- brown. G=4.09 (Cb,Ta)2Os,Y2O3. hedral. 1.826 Malacon...... Sq. prisms...... Colorless...... H=3 Altered zircon. ZrOz-SiOs-raHiiO G= 4.0 to 4.3 1.83 Isomet. Oct...... Yellow...... H=5.5 Insol. in acid. F=dif. Opt. anom. with low B. SCaO-SSbsOs G=5.04 1.83 Isomet. Cubes . . . {100> perf...... Colorless...... H=3 to 4 Sol. in acid; somewhat sol. in H2O. Rapidly alters CaO G=3.32 on exposure to moist air. 1.830 Isomet. { 1 1 0 > , {110} poor...... Dark red, etc...... H=7 Garnetgroup. Insol.inacid. F=3. Data for pure 3FeO.Al2O3.3SiO2 <211>, etc. G=4.250 mineral. 1.838 .....do...... None...... Emerald-green.... H=7.5 Garnet group. Opt. anom. Insol. in acid. Infus. 3CaO.Cr8O3.3SiOs G= 3.418 Data for mineral with percentages of A12O3=5.9, Cr2O3=22.5. 1.865 .....do...... Varies...... H=7 Garnet group. Gelat. imperfectly. F=3.5. Data 3(Ca,Mg,Fe)O.Fe3O8.3SiOs {211},etc. G= 3.781 for mineral with percentages of Al2Os=6.1, FesOj=25.1, FeO=0.8, CaO=33.7. 1.86± Gray, green, etc... H=4 F=3to4. Hydrous antimonate of Pb. G=4.8± 1.87± .....do...... Yellow...... H=5.5 Insol. in acid. F=dif. Opt. anom. with low B. 5(Ca,Mn)O.3SbaOs G=5.07 1.87± .....do...... Grayish brown.... H=5to6 Near pyrochlore. Contains Cb, Si, Zr, Ce, Ca, Na, G = 3.77 F,O,etc. 1.88 Tsch6ffkinit6 Yelvet-black...... H=5 Gelat. F=4. Red-brown in section. Inpartbire- Titanosilicate of Ce, Fe, etc. G= 4.3 to 4.55 fracting and opt. . 1.895 Isomet. {110}, . ....do...... Yellow, green, H=7 Garnetgroup. Gelat. imperfectly. F=3.5. Data 3CaO.Fe2Os.3SiO8 {211}, etc. brown, black,etc G= 3.750 for pure mineral.. 1.9± Stibiconite...... do...... Gray,yellow,etc.. H=4to5 Insol. in acid. Infus. SbsO^.nHsOC?) G=5 1.92± .....do...... Greenish black.... H=5 Columbate and titanate of ura­ G=4 nium, etc. 1.925 .....do...... Yellow, brown,red H=5.5 Pyrochlore group. Decpd. by H2SO<. Infus. Ou 6CaO.3TaaO5.CbOF8 etc. G=5.-51± ignition n changes to 2.040. CO TABLE 7. Data for the determination of the nonopaque minerals Continued. oo Isotroplc group Continued. o

Crystal system and Hardness and 71. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks.

1 Q1 {100}...... H=2 Sol. in HSO. Fus. Oxidizes rapidlv. Data on cu^ciy - G=3.93 artificial crystals. 1 Q4. Black...... H=7 Garnet group. Gelat. F=4. TiO 2=8.7percent. o 3CaO.(Fe,Ti)203.3(Si,Ti)0 2 {211 >, etc. G=3.7 1.94 Friable Columbate of U, etc. G=5.24 . 1.96± .....do...... H=5to6 (Ta, Cb)2O5, H2O,etc. G=5.19 1 Qfi .....do...... H=5 Pyrochlore group. Decpd. by H2SO4. Infus. On 'Columbate and titanate of Ce, G=4.3± ignition n increases to 2.000. Opt. anom. Ca, etc., with Th, F, etc. 1.965 Tscheffkinite...... Conch...... Velvet-black...... H=5 Gelat. F=4. Red-bro%vn in section. In part bi- Titanosilicate of Ge, Fe,etc. G= 4.3 to 4.55 refracting and opt. . 1.9R± Brown...... H=5 Tantalocolumbate of U, Ca,etc. G=4.8± 1.98 Black...... H=7 Garnet group. Gelat. F=4. TiOs= 16.9 per cent. 3CaO.(Fe,Ti)2O3.3(Si,Ti)O2 {211V, etc. G=3.85± 1.99± .....do...... H=4to5 Sb2O4.reH2O(?) 0=5 £ 2.0± Wiikite...... do...... Black...... H=6 Columbate, titanate, and sili­ G=3.8 to 4.8 cate of Fe and rare earths. 2.00 {111} variable..... H 5 Columbate and titanate of Ca, G=4.3 ignition n= 2.227. Ce, etc., with Th, F, etc. 2.01 Black...... H=6 Near schorlomite, etc. {211}, etc. G=3.7 2.05 {100}...... H=2 PbO.CuCl2.H2O G=5.25 TABLES FOR DETERMINATION OF MINERALS. , 181

O) a 'S -4 CVO ri i_ fl 9-P .2 W I o u s b ^ u ^ b/} 0 § ® CS 5 8 i £ 8 a « ! 2 a* " CN A « .a t< .3' 1 PI W p gR « 0} ' 1 a X! id 1 1 a ^ ?g 3 CO 0 d ^ f « 1 rt. a ^ 1 1 ad T!|g| *o 1 6* 1 1 : 3 tt fn .9 -a CO ^ ^PQ Ui : >-> ra O" 2? 1 4JID 1 1« . i 1 s O .® « W tt- .fl .3 ii - CO d A ^ Inabnormallybirepart Opticanomalies.F=2. '.in.acid.Infus..Insol. dishbrownpowderin SpinelInsol.iigroup. flame.Nearlyopaqui HCI."Sol.F=1.5,invo HzSOi.InftDecpd.by hotsol.inEasilyconct. IBlomstrandinegroup. Sol.Sectile.inammonj . Insol.acids.F=dif.in withanisotropicn=2.. acid.EasilyinFsol. Sol.H^Oi.Infus.in birefracting.faintly Blomstrandinegroup. HCI.Infus.Sol.in. 1red-brown.section red-brown.Insection

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CO ^ 4* - « H ^ ^H SCO ^ SH" "3 ^N W P *S :£ " 3 Columbiteof Hydroustitai Th,Y,Er, iYttrotantalite_. >i«-«5 O i43« W*i^ SfiTiarmnTitit.fi Yttrnnmsitfi ol »-f^, Xi a 18 a FeO.CrO23 flfll T7.iilvt.itP Oca" . §§ 'So 1 |S" I 4 * o" |«r §« i ffif-i « o^> 5 -S 1« 1^" g 0 PO .§fH E 3W !§ jw | OQ ^^ feC g 3 ^ S o S c CQ PH < -H H ^ -H -H -* »o i< CN < - w e S-H «» f >» U9 3- 2, g S S § sis i l-l r- r- *H rn t> CN1 CN C> (N CNi CN CN (N- (N CN CM CN d TABLE 1 . Data for the determination of the nonopaque minerals Continued. 00 Isotropic group Continued.

Crystal system and Hardness and n. Mineral name and composition. habit. Cleavage. Color. specific gravity. Remarks.

2. 15± H-5.5 2(Ca, Ce,etc.)O.CbsO5.2/5NaF G=4.5 section red. 2. 15± Embolite...... H=l to 1.5 Ag(Br, Cl) G=5.4 cerargyrite and bromyrite. Sectile. 2.16 H=5.5 FeO.Cr2O3 Massive. brownish black. G=4.5 flame. 2.16 ...... H=5.to6 MnO nearly black in G=5.18 emerald-green. mass! 2. 17S± Fergusonite...... Ps. tetrag. Py­ { lll}imperf. Conch. Black...... H=6 Decpd. by HjSO4. Infus. After ignition becomes (Y, Er, Ce)2O3.(Cb, Ta)2O5 ramidal. G=5.8± B. with w=2.142. Uhligite...... { 100 }imperf...... do...... Near zirkelite. Translucent on thin edges. CaO.AhO3.ZrO.2TiO2 2.19 Zirkelite...... do...... do...... H=5.5 Insol. in acid. Infus. Clear reddish brown in (Ce, Fe, Ca)O.2(Zr, Ti, Th)Os 0=4.72 section. 2.195± Ps. tetrag. Py-...... do...... do...... H= 5.5 to 6 Decpd. by H2SC>4. Infus. On ignition becomes (Y, Er, Ce)5O3.(Cb, Ta)2O5 ramidal. 0=5.8 anisotropic with n= 2.090. 2.195± Euxenite ...... ;..... Ps. orth...... do...... Brownish black . . . H=6.5 Blomstrandine group. Insol. in acid. Infus. In Columbate and titanate of Y, G=4.8 section reddish brown. After ignition n=2.23. Er, Ce, U, etc. OldJwnjtfi ,, ... ,,, , {100}...... H=4 CaS G=2.58. 2.20 {111} nearly perf H=5.5 5CaO.2TiO8.3SbjO5 col ophony- G=4.95 brown. 2.20± H=4to5 Bi2Q8.COa.nHjO G=7± crystalline. 2.20± Black...... G=9.32 ThO8,U8Oa, etc. 2.20 .....do...... {lll}dist...... H-l 2AgCl.2AgBr.AgI low. G=5.7 F=l. Sectile. 2.20 I H=2 Sol. in ammonia. F=l. Tw. pi. {111}. Sectilc. CuI.4AgI etc. G=5.64 2.205 Conch...... H=5.5 Insol. in acid. Infus. In section reddish bro\vn. 2(Ca.Fe)O.2CeaO3.STiO2. G=5.0± 3Cbs05 2.21± Ps.orth. Pris.... {010} imperf. H-5to6 Nearly insol. in acids. F=5. In section brown­ 3(Fe.Ca,UO!,etc.)O. Conch. G=»5.6to5.8 ish to opaque. Sensibly isotropic to strongly (Ce,Y,etc.)2Os.3(Cb,Ta)jO5 birefracting. 2.215 .....do ...... {100} {010} tr. Black...... H-6.5 Infus. Reddish brown in section. Columbate, titanate, zirconate Conch. G=4.8 of Ce, etc. 2 O4J_ H=6.5 Blomstrandine group. Insol. in acid. Infus. In Columbate, titanate of Y, Er, G=5.0± section reddish brown. U,Ce,etc. 2.25± Ps.orth...... {010} imperf. Black...... H=5to6 Nearly insol. in acid. F=5. In section brownish 3(Fe,Ca,UOs,etc.)O. Conch. G= 5.6 to 5.8 to opaque. Isotropic to strongly birefracting. (Ce,Y,etc.)20,.3(Cb,Ta),06 2. 18 red H-5.5 Sol. in acid. Infus. 2. 39 blue NiO black. G=6.4 2.253 {110} poor...... H-2 Sol in ammonia. F=l. Sectile. Agfir etc. G=5.9 2.26± Ps. ortli ...... H=5 Insol. m acid. Infus. Reddish brown in section. 2(Ca.Fe)O.2CesO3.STiOj. G=5.1 On ignition becomes birefracting with n= 2.285. 3Cbj>O6 2.26± H-4 Effervesces in acid. F= 1.5. BitOi.COf.nHjCK?) G= 6.9 to 7.7 {lll}dist...... Insol. in acid. Fuses to a black slag. Weakanom. 3RO.SbiOs. R=Pb:Fe=3:l brownish green G= 6.58 to 7.29 B. to brown or black. 2.30 Ps. tetrag...... Black...... H=»7 Sol. in acid. Light reddish brown in transmitted p Chiefly TiOj,UO8,UOs, G=5.1 light. W ThOj.YjOs, (Ca,Fe)O. 2.30 {100V...... do...... H=5 Near perofskite. Brownish in powder. Anom. B. (Ca,Y,Fe,Ce)O.TiO, G=4.2± with B=low. 2.33 .....do...... do...... H-5to6 Near perofskite. Compare with the pyrochlore 7(Ca,Ce,Fe,Naj)0. G=4.13 group (pp. 179-182). Decpd. by HC1 with diffi­ 6TiOj.Cb2O5 culty. Infus. Nearly opaque. In part aniso- * ^ tropic, with B=weak. OO TABLE 7. Data for the determination of the nonopaque minerals Continued. oo Isotropic group Continued.

Ig I Crystal system and Color. . Hardness and n. Mineral name and composition. habit. Cleavage. specific gravity. " ' ' Remarks. Q

2.346 Isomet. Tetrah . {110}...... Oil-brown, etc. . . . H-2.5 Cu2Is G=5.59 2.35u H- 6 to 6.5 MgO.Fe2O8 an powder. Q=4.& : transmitted light dark red. Q 2.36i.i± FniTilrlinita- .....do...... do...... H=6 (Zn, Fe,Mn) O . ( Fe, Mn )SO a O=5.1.--. opaque in reddish brown. 2.37Na ' {110}perf...... H- 3.5 to 4 2.34Li ZnS (pure) yellowish. G=4.0 pure ZnS. 2.38 -H-5.5 CaO.TiO2 G=4.03 with complex tw. 2.419 2.72U None...... H=3 .'. ; , Decpd. by HNO8. F=1.5. In section bright red 5Cu2S.2ZnS.2Sb2S8 Massive. Tw. Wack. .G=,4.6ib. ' to opaque. . pi. <111> and ?100>? >2.72i,i \H=43 1 5Cu2S.2ZnS.2As2Sa etc. red in splinters. G=4.6± ' Uniaxial positive group. [The greater part of the minerals of this group are tetragonal or hexagonal, but some minerals that are strictly biaxial but with nearly zero axial angle are included here as well as in their proper biaxial group. A considerable proportion of these biaxial minerals with nearly uniaxial optical properties have also nearly hexagonal crystal form.]

Hardness and e « Mineral name and composition. System and habit. Cleavage. Color. specific gravity. Remarks.

1 ^i^ i ^no Ice...... H=1.5 H2O G= 0.917 1.378 Sellaite...... Tetrag. Pris...... <100}{nO}perf...... do:...... H=5 Sol. in conct. H2SO4. F=4~to 5 with in­ MgF2 G=3.0jb tumescence. Fib. c. Opal-like. H=*2± Decpd. by acid. Infus. Pleoc. faint: o>= CuO.SiOj.nHaO G=2 nearly colorless, «= pale bluish green.

1.0 red {0001}perf...... Indigo-blue, streak H= 1.5 to 2 Sol.inJHNOs. F=2.5. Translucent only 1.45No CusS .nearly, black. G=4.6 in thinnest plates. ,In transmitted light green and pleochroic. l.SOri H 1.57 1.46± ChrysocollaC?) ...... Fib. c. Opal-like. Beryl-blue...... H=3 I)ecpd. by acid. Infus. Pleoc. faint: CuO.SiO2.2H2O ,G=2.4 u colorless, «== pale bluish green. 1. 474 1.470 <10lO}dist...... White...... H=4.5 Zeolite group. Decpd. by HC1. F=3. (Na2,Ca)O.Al2O3.4SiO5.6H2O G=2.1 . 2V small to 0. Tw. axisc. 1.47 Orth(?)...... do...... Sol. in alcohol and other organic liquids. Hydrocarbon. G=0.95 F= very easy. Bums. . 1.486 1.475 Mon.(?) Fib. c...... do...... H=5 A zeolite. Decpd. by warm conct. HC1. 2CaO.Al2O3.5SiO2.6H2O G=2.2 ; Fuses to a blebby glass.

1 4QO 1 4£ft {10Tl}dist...... do...... H=4.5 (Ca,Na2)O.AlgO3.4SiO2.6H2O G=2.1 ration of slimy silica. F=3, with in­ tumescence. 2V small to 0. 1 48' Oct......

00 Cn TABLE 7. Data for the determination of the nonopaqtie minerals Continued. OO Uniaxial positive group Continued.

Hardness and c u Mineral name and composition. System and habit. Cleavage. Color. specific gravity. Remarks.

1.499 1.491 Aphthitalite ...... {lOlOM-ather dist.. White...... H=3 Glaserite. Sol. in H2O. F=1.5. (K,Na)2O.SO3 rhombs. <0001>imperf. G=2.69 1.550 1.502 Paraffin...... Plates and fib...... do...... H=l Hydrocarbon. G=0.9 Lies on base on crushing below cover glass. 1.509 1.508 Leucite...... Ps.isomet.{211}... <110>poor...... H=6 Decpd. by acid. Infus. Inclusions K2O.Al2O3.4SiO2 G=2.5 characteristic. 2V small to 0. Poly, tw. lamellae. 1.54 1.515 Orth(?). Fib.... White...... H-l Hydrocarbon. G=0.9 Elongation of fibers is . Lie on base. 1.522 1.518 Leiflte...... Hex. Pris...... Pris...... H=6 2Na2O.(AlF)O.9SiO2 G=2.57 1.621 1.518 Davyne ...... Hex...... <10lOX0001}perf... H=5.5 4(Na,K)2O.Ca0.4Al2O3.9SiO,. G=2.4± crinite. Gelat. Fuses with intumes­ 3H2O.2CO2? cence. 1.529 1.521 .....do...... <10lO}perf. {0001} H-6 3(Na,K)2O.4CaO.6Al2O3. less so. G=2.4 F=difflcult. 12SiO2.S03.4(Na,K)Cl 1.527 1.522 Natrodavyne ...... do...... {10lOK0001}perf...... do...... H=6 Near davyne but with no K G=2.50 and much CO2. 1.575 1.533 Fibroferrite...... Orth(?) Fib. c... H=2 Fe2O3.2SO3.10H2O G=1.86 Pleoc. feeble: u= nearly colorless, «= pale yellow. 1.537 1.535 Apophyllite ...... Tetrag ...... {001}perf.{110}less H=5 KsO.8CaO.16SiO2.16H2O so. G=2.3 tion of slimy silica. F=2. Opt. anom. 1.553 1.544 .....do...... H=7 Si02 and pyramids. G=2.66 1.556 1.550 Trie...... {lOlOXlOllKOlll} H=2 Sol.inH2O. F-4.5to5. Tw. pl.(OOOl). FejOs.3SOj.9HiO imperf. let. G=2.1 Abnormal interference colors. TABLES FOR DETERMINATION OF MINERALS. 187

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Hardness and g( 1 < < > Mineral name and composition. System and habit. Cleavage. Color. specific gravity. . Remarks. O O en 1. 590 1.589 Rinneite...... Trig...... {1010}<1120>fair.. Colorless,rose, yel­ H=3 Sol. in acid. F=easy. O FeCl2.3KCl.NaCl low. G=2.35 O 1 I B=very 1.59 .....do...... Yellow...... H=2.5 Deliquescent. Readily fus. O weak. 4KCl.MnCls G=2.31 a 1.612 1.697 Amesite ...... Ps. hex. Plates. . 'Pale bluish green : H=2 to 3 Chlorite group. Decpd. by HC1. Infus 2(Mg,Fe) O . Al2O8.SiO2.2H2O G=2.77 but swells on heating. MgO :FeO=5:l.. 1.615 1.604 Tetrag. Cubo-oct. H=6 Melilite group. Gelat. F=3. Anom. 3CaO.Al2O3.3SiO! G= 2.4 to 2.9 biax. 1.611 1.606 Hex...... {0001} dist.{ 1020} H=5 Gelat. F=3. Opr. anom.; Pleoc.weak. 6Na2O.6(Ca,Fe)O. poor. G=3.0 Abs.: o;> . 20(Si,Zr)O2.NaCl B=0.02 1.615 .....do ...... {0001} perf...... Reddish yellow... H=4 'Sol. jn acid. Infus. (Ce,La,Di)F3 G=5.8± 'H=3 1.654 1.620 Rectangular tab­ {001}perf...... Smoky gray tinged Sol. in acid. Infus. Z (or e) is normal 3CaO.5Ce2O3.6P2O».24H2O lets beveled par­ with red. G=3.14 to the tablets . allel to the long edge. B weak 1.625 Qeorceixite...... Trig.? Microcryst. Brown, white, ete . H=6 Alunite group. (Ba,Ca,Ce)O.2AlaO3. G=3.10 P2Of.5HsO 1.630 1.620 Goyazite...... Trig. Tab. { 0001 > {0001} perf...... H=5 Alunite group. Insol. in acids. F=4. 1.639 1.629 2SrO.3AlsO3.2P,O».7H8O ,G=3.20to3.26 Zonal growths. Basal segments com­ monly show anom. B. in hexagonal segments. Pleoc.: o>=red-brown, «= yellow. 1.639 1.633 Akermanite...... Tetrag...... {001}, {110}...... do...... :;... H=5 Melilite group. Gelat. Data for pure 4MgO.8CaO.9SiO, G=3.12 mineral. B=0.01 1.64 <0001}perf...... H=5 Alunite group. Difficultly fus. Nearly 2SrO.3AljO3.PjOt.2SO3.6HjO G=3.52 insol. Basal section divides into six biax. segments. TABLES FOR DETERMINATION OF MINERALS. 189

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( a Mineral name and composition. System and habit. Hardness and Cleavage. Color. specific gravity. Remarks.

1.803 1.794 Arseniopleite...... Trig...... 9(Mn,Ca,Pb,Mg)O.(Mn,Fe)sO3. chroic. 3AsjOs.3H2O High. Thorite...... <110}dist...... H-5 Th02.Si0 3 mids. brown, orange. G=5.3 monly isot. from alteration. B-0.04± 1.865± H-4.5 2Cej03.3Sr0.7CO2.5H2O bic pyramids. low - green, or­ G=3.95 Infus. ange. 2.12 1.90 Trippkeite...... <100> highly perf. Soft Arsenate of Cu. {110>less perf. break up into flexible, asbestos-like pieces. Bluish-green in section and nonpleochroic. 1 045 1.910 , {10lO}im- H-4 5PbO.4CaO.PbCl2.6SiO2 perf. G=5.43 1.934 1.918 Scheelite...... . CaO.WOs tab. brown, gray. G=6.12 G=6.12 for pure mineral, but de­ creases to 5.94 for mineral with 8 per cent MoOs. Gives a deep-blue color when powder is boiled with HC1. and again ooiled after zinc or tin is added. 1.968 1.923 H=7.5 2.015 1.960 ZrO2.SiO2. prisms and pyra­ ] ow, brown, G= 4.5± mids. gray, pink, etc. 1.971 1.945 Hex. Pris...... {0001}, {1010} im- White...... H=3 F=easy. 5PbO.4CaO.PbCl2.6SiO2 perf. G=5.43 1.96 Dixenite...... Hex. Plates...... {0001}mic...... Black...... H=3-4 5MnO.SiO2.As2O3.H2O G=4.20 mitted light. 1.978 1.967 Powellite...... _ ...... H=3.5 CaO.(Mo,W)0? low. G= 4.35 to 4.53 1.973Nll Calomel ...... {100} {111} rather H= 1 to 2 Sectile. Insoi. in . Volatilizes at 1. 2.601ia Hg2Cl2 disi. G=6.48 2.093 1.997 .....do...... {lOOHlli}imperf. Brown, black, H=6to7 Insol. in acid. Infus. Tw. {110} poly- SnOj gray, white. G= 6.8 to 7.1 synthetic. Anom. 2E. Becomes coated with metallic tin when em­ bedded in granulated zinc and HC1. 2.029 2.008 Zincite ...... Hex...... <0001>perf...... Deep red...... 11=4 Sol. in acid. Infus. Streak orange-yel­ ZnO G=5.68 low. Section deep red, nonpleochroic. B rather 2.03± Voltzite...... Hex. Spherical Yellowish, r e d - H=4 Decpd. by acids. Infus. strong. ZnO.4ZnS globules. dish, brownish. G=3.7 2.140 2.114 Tetrag. Pris. tab.. {110}{100}dist.... White, gray, yel­ H=3 Sol. in dil. HNO3, with effervescence. PbO.PbCl2.C'02 low. G= 6.0 to 6.3 F=l. 2.21 2.13 Hex. Prisms..... {000l}dist...... White...... Sol.inHNO3. F=l. Pb0.2PbCls B=0".01 2.182 Hex. Thin plates. {0001} perf...... Yellowish, green­ H=ltol.5 Sectile. Sol. in NH=pale yellowish or red­ dish brown, «=nearly opaque. Indices for mineral with G=7.4. 2.4U 2.3=brown, «=green FeO.(Ta,Cb)sO5.4TiO, G=5.56 and nearly opaque. May be opt. . 2.529N. 2. 506N. Hex. Short {1120}dist.,{000l> H=3 to 3.5 Sol. in HC1. Infus. Data for pure arti­ 2.456i,i 2.43Ui CdS 1 prisms. Crusts. indist. G=5.0 ficial crystals. 192 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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§0 -al «S- '°. -1 >0>4 COM' co'ei CO CO %Z w & || n 17 II II I'D 1? Ho Wo KO Ao KO Ko MO BO W 05 ** d J ; 11 1 J2 lyuniaxial.O] g 3 "3 strictlyrtare Carmine-red White...... Colorless... o s § . ~ o c * * C e I i: White < g * aO, ^ o 0 S § C" ; M "s > 8 .2 13 bo d et o minperf.{010}dist. {10lO}easy. 'Cubictr. . 1 Uniaxialne ralswhichh 1- 5 5c 5*8 '5o o s S bo V i I 0< o Hex.Short i ^ -S 1 hexagonal,onalbor Fibers...... 03 S biaxialofthesemine S w'*5 ^ s S S W) J O o -g § 03 "a prisms. bl E 5P+i ^ i 1 2 a » a gfi «H CQ i ft CS ^* mposition. :o :o |l W :o o. 6*1 i w ;O ;0 8 .£a : :o :o :o ;O : : SI ;<< Q !§ s ' CO :o Villiaumite. Mendozite.. Hanksite... aj mineralsofie Chiolite..... 2NaF.AlF NasO.Al02 Gmelinite... Chabazite... UNajO.QS Cristobalite. Analcite.... § theirbproper (Naj,Ca)O (Ca,Na2)O Mineral Moissani '"Se CSi 1 NaF Si02 3 W

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1.537 1.535 Tetrag...... <100>perf. {110} H=6 Scapolite MawoMeo, low in CO2. Insol. in 3NajO.3Al2O,.18SiOj.2NaCl less so. 0=2.56 acid. F= 3 to 4. C12 may be replaced by CO» and SO4. CO2 "increases the birefringence. 1.510 1 540 Hex. Tab.-{0001}. <0001}mic...... H«=2to3 Near pyroaurite. Hydrotalcite group, 6MgO.FeaO8.COj.l2HsO Pearly luster .... G=2.07 Sol. in acids. Infus. Pleoc.: «= yel­ low red, «= colorless. 1.538 1.542 Hex...... <10lO}dist. {0001} Colorless...... H=6 Nepheline group. Gelat. F=3.5. Lus­ NaiiO.Al2O3.2SiOj imperf. G=2.6 ter greasy. 1.516 1.542 Hex. Plates<0001> {0001 }mic...... Green...... H=1.75 Hydrotalcite group. Sol. in acid. Infus. 6MgO .CrsO».COj. 12H»O G=2.16 Anom. biax. Pleoc. weak. Abs.: w>«. 1.545 <0001}dist...... G=2.67 NepheUne group. Gelat. LisO.AUOg.2SiO, 1.503 1.545 Pholidolite...... {001>mic...... Grayish yellow. . . . H=4 Nearly colorless in section. Biax. with KjO.12(Mg,Fe)O.Al2O8.13SiOj. G=2.41 2V small. 5H,O B=0.01 1.545 {0001 }mic...... White, etc...... H=3to4 Zeolite group. Decpd. by HC1. F= dif­ 4CaO .6SiOs.5(H,Na, K)SO lae. G=2.43 ficult. 1.538 1.551 Colorless, etc...... H=6 Scapolite group. Data for MaTsMeas, low Scapolite. {110}ress so. G=2.61 in CO2. Insol. in acid. F=3. CO2 increases the birefringence. B-0.01 1.555 Soft MgO, AlaO«,SiO2,HsO G=2.26± 1.54 1.560 <0001}mic...... H=1.5 A vermiculite. Altered mica. Decpd. 5(Mg,Fe)O.2(Al, Fe)2Ot.5SiO,. brown, etc. G=2.30 by HC1. When heated at 300° C. it 11H2O(?) exfoliates very remarkably; on higher heating it becomes pearly white and ultimately fuses to a dark-gray mass. 1.560 1.565 Trig...... do...... H-3 Zeolite group. Gelat. F=very easy. 3CaO .CaF,.3SiOj.2H»O G-2.76 Biaxial borders. 2V=0 to 27J" and disp. p<«. B=0.01 1.565± Hex. Tab. {0001} {0001 >mic...... White, etc . H=2to3 Hydrotalcite group. Sol. in acid. Infus. 6MgO.FejOj.COs. 12H3O Fib. Pearly. G=2.07 Pleoc.: o)= yellow red, =colorless. 1.564 1.568 Beryl...... H-8 Insol. in acid. Infus. Pleoc. variable. 3GlO.AlsO3.6SiO2 blue, etc. G=2.66 Data for mineral with NajO=0.43. 1.545 1.567 H=5to6 Scapolite group. Data for MasoMesq, low Scapolite. 110} less so. G=2.65 in carbonate. Insol. in acid. F=3. The carbonate scapolitc has a stronger birefringence. B= weak 1.57 Not stable. FeCls 1.57 1.575 M o n . ? Scales, H=2.5 Easily decpd. by HC1. F=easy. 6CaO.3FejO8.4PsO5.19H2O nodules. G=2.53 1.577 1.579 <001}perf...... H=2 Chlorite group. Decpd. by 5(Mg,Fe)O.Al3O8.3SiO2.4H3O and shreds. G=2.7 F=dif. Biax. with 2V7=0±. Pleoc.: X nearly colorless, Y and Z green. Abnormal blue interference color. 1.575 1.581 Bervl...... Hex. Pris...... <001}imperf...... H=8 Insol. in acid. Infus. Pleoc. variable. 3GlO.Al2O8.6SiOa blue, yellow. . G= 2.714 Data for mineral low in alkalies. 1.551 1.582 <100}perf...... H-6 Scapolite. Data for Ma^MeTs, low in Scapolite. bluish, reddish. G=2.69 carbonate. Decpd. by acid. F=3. 1.560 1.586 Tetrag. Ps. orth. {001}...... Yellow...... H=2to3 Sol. in acid. Fus. See biax. . Pleoc.: CaO.2U03.AssO6.8HsO Rect. tablets. G=3.45 w=pale yellow, t= colorless. 1.336 1.587 Trig...... <10ll>perf...... White...... H-2 Tastes cooling. Soluble in H»O. F=l. NasO.Ns06 G=2.27 Deflagrates on heating. 1.573 1.591 Yellow...... H=2.5 Sol. in acid. Partly sol. in H2O. F=5. o(K2.Na2,Fe) O.SFeaOj. 12SO8. G=2.53 Pleoc.: < >= yellow, «= green to nearly ISHsO colorless. 1.56 1.59± <0001}perf...... H- 2.5 to 3 Faintly pleoc. 2NiOs.3SiOs.2H2O G=2.5 1.582 1.592 {001}mic...... H=2 Luster on (0001) pearly. Sol. in H2SO4. CuO .2UO8.PsO6.8?H2O Tab. {001>. G=3.5 F=3. 1.585 1.595 Fib...... White...... H=4 Pseudomorph after goyazite. Sol. in CaO.2Al3Os.P3O6.5HsO acid. B. b. decrepitates and fuses. 1.560 1.597 Meionite...... <100}perf.<110}less H=5.5 Scapolite. Data for MaoMeioo. Decpd. 4CaO.3Al2O3.6SiOii.(COj!,SOs) so. G=2.74 by acid. F=4.

Oi TABLE 7. Data for the determination of the nonopaque minerals Continued. CO Uniaxial negative group Continued.

Hardness and c Mineral name and composition. System and habit. Cleavage. Color. specific gravity. Remarks.

1.590 1.598 Beryl...... {0001}imperf...... Colorless etc H-6 3(Gl,Na3)O.Al2O3.6SiO 3 G=2.80 Data on mineral high in alkalies. 1.600 Biotite ...... <001}mic...... H-3 K30.4(Mg,Fe)O.2(Al,Fe)203. G= 2.7 to 3.1 cultly fus. Pleoc. marked in brown or 6SiO2.H3O green, Abs.: Xdist...... Yellow H-5 2Ca0.2G10.3SiO3.NaF pyramids. G=3.01 biax. 1.607 1.613 <0001>perf...... H- 4.5 to 5 (Ce,La,Di)F3 G=5.6to6.1 1.609 1.620± Dahllite ...... Hex. Fib....---- H-5 7CaO.2P2O».CO2.JH2O G= 2.87 to 3.05 1.619 1.621 Gillespite...... H-3 BaO.FeO.4SiO2 G=3.33 strong: w= very pale pink, «=deep rose red. 1.618 1.621 Trig...... H-5 6NasO.6(Ca,Fe)O.20(Si.Zr)O2. poor. red, etc. G=3.1 NaCl B=low. 1.625 Ps. hex. Fib.---- H-4.5 Apatite group. Sol. in HNO3 or NIUOH. 10CaO.3P2Oj.CO2.CaFz.H!1O G=3.1 F=easy. Basal section shows iix biax. segments. 1.605± 1.626 H-6.5 Silicate of Sc, etc. G=2.8 and opaque b. b. Pleoc.: < >= very pale greenish yellow, «= intense azure blue. 1.582 1.627 <100}perf., {100} Soft 3TJO3.As3O5.12H2O lets < 001 >. good. G=3.3 1.613 1.632 Dravite...... Hex. Pris...... None...... Brown to black . . . Magnesian tourmaline. Insol. in acid. Na2O, ( Mg, Fe) O, A13O3, SiO2, 0=3.1 Fus. Pleoc. Abs.:w>e. B2O3,H3O TABLES FOR DETERMINATION OF MINERALS.

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i J o !< i *7tio ; 2S i iPi fW>*3 ^ d I .s 5 1 1 15 : 8 i » c> *Si Si ^»S 0) rt Cr M ^H o 2 2 c § v* O O ij 8 8 8, / 1; ^v~ -V* ^ 5? *V ^ *v- s aT 1 : J XI : en : i 1 S * § *^ ^ 3 55 ' ^ 3 +3 g X 8 o i i .g 1 S| I. PH fc SPH HHW (>1 hff'i* 1 to OJ _r~\^^ 60 _J- td go j 0-^5 4jO u (5 ® a) a og tS"v* w' otc o"^ s & s H W W s W o : ' 0 :o :o ^ : : co :o ; c : 1 (-! ft. S :§ '"? ra ;o O o" ' £, Chalcophyllite.. O.14H7CuO.Asi26 bo ' C8 Lepidomelane..... Zeunerite...... CuO.2UOO.As25. Elbaite...... Daphnite...... O27FeO.10Al 1823. Bementite...... 10MgO.4BO.3Hii32 WUkeite...... 4MnO.3SiO(.3H2 - « lo 7CaO.2PO6.CO2 Iron-richbiotite. Jeremejevite...... SiOO8,AlO,l,B23 5MnO.4SiO.3HC2 Szaibelyite...... 19CaO.3PO.CO25 o^ '' I t. 1 co c? ;Pn A1.BO32 Mfililitp. qo |

CO CO § i i s s i i a 1 S s S 1 s 8

iO cD § "g CN W *T C1* O »O E5 S CO CO -Js s-; Sn Iii CQ n TABLE 7. Data for the determination of the nonopaque minerals Continued. Uniazial negative group Continued. OO

Hardness and e Cl) Mineral name and composition. System and habit. Cleavage. Color. Remarks. o specific gravity. w o CO 1.486 1.658 Calcite...... Trig...... {10ll}perf...... H-3 Effervesces in acid. Infos. Data on O CaO.COj G= 2.715 pure CaCOs. o 1.660 Fermorite ...... H-5 o 9(Ca,Sr)O.(P,As)2O6.Ca(OH,F)2 G=3.52 acids. Infus. 1.629 1 664 Friedelite...... Trig. Tab. {0001}. {OOOlVperf. -{10TO> H 4 9(Mn,Fe)O.8SiO2.MnCl2.7H20 imperf. G=3.07 Nearly colorless in section. Thick plates plcoc. Abs.: «. Opt. anom. with small 2V and optic plane {112"0}. 1.661 1.666 Gehlenite <001}imperf...... H-5. 5 Melilite group. Gelat. F=6. Data for CaO,MgO,Al2O8,SiO2 G=3.04 mineral with percentages of akerman- ite=20, velardenite= 80. 1.658 1.669 Velardenite...... H-6 2CaO.Al2O8.SiO2 G=3.04 pure artificial mineral. 1.638 1.669 Schorlite...... Black...... H-7 NasO, (Fe, Mg)O, A12O8, SiO2, G=3.22 o>>e strong. B2O8,H2O,etc. 1.657 1.669 <001}good, <100>, T\ru*4-rt H-3 Gelat. F-dif. 2CaO.ZnO.2SiO2 OlO}rare. G=3.4 1.636 1.675 Pyrosmalite...... Trig...... {0001>perf. {1010} H-4 Decpd. by acid. F 3 to a black glass. 9(Fe,Mn)O.8SiO2.FeCls.7H2O poor. brownish. G=3.1 Nearly colorless . in section. Thick «. d 1.59 1.675 Chloromagnesite...... Soft...... MgCls

1.500 1.681 {1101}perf...... White H-4 * CaO.MgO.2CO2 G=2.87 Infus. Data for pure mineral. feJ W 1.652 1.685 Schorlite ...... H-7 NasO, (Fe,Mg)O,Al2Q8,SiO2, G=3.2 Abs.: < )>« strong. £ B2O8,H2O,etc. VI 1.641 1.687 Tourmaline...... do...... do...... Black...... H-7 NasO, (Fe.Mg.Cr)O, A12O8, G=3.3 Fus. Pleoc. strong: o>= green to bluisjj SiO2,B2O8) H2O,etc. green, e= yellow. TABLES FOB DETERMINATION OF MINERALS. 199

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2(Fe.Mg)O.(Fe.Ai)a6.5S8 Gehlp.nitft.__.__-______.. (Ai,Fe)(OH,F)O.2SiOs Ce,Y,Ca,Silicateetc.,of Hematolite...... 8MnO.(Al,Mn)s.O8.ASjiO5. OSiOCaO,MgO,A132, (AlCl)O.6CuO.SOO.9H8s Ankerite...... Pvrnr.hroite_----.--.--.-. tainingfluorineandboi CaO.(Mg,Fe)O.2COs CaO.(Mg,Fe)O.2COs (Ca,Mg,Fe)O.CO2 9CaO.3AssO.CaF25 Vfisiivianite___._____ 2(Ca,Mn,Mg,Fe)O. Mp.laTin..p.r1t.p.______(Mg,Fe)O.CO8 MgO.COa Ma_mp<;it.p._ KvfthitP..___. q O3H3 Snantrnlite Dnlmnite AnVAritfi. tr? ' S 1 *J

t-t--88 _-2 TABLE 7. Data for the determination of the nonopaque minerals Continued. fcO o Uniaxial negative group Continued. o

Hardness and e 0) Mineral name and composition. System and habit. Cleavage. Color. specific gravity. Remarks. §en 1.547 1.749 Ankerite...... <10Tl}perf...... White...... H=4....._...... Sol. in acid. Infus. Data for mineral with O CaO.(Fe,Mg)O.2CO2 G=3.12 peicentages of CaCOa=48.3, MgCO3= O 11.3, FeC08' = 37.9, MnC03=2.5. >tf h-t 1.63 1.76 Black...... Chlorite group. Decpd. by HC1. F=4.5. O 2(Fe.Mg)O.(Fe,Al)2O8.5SiO2 . G= 2.71 to 3.4 Strongly pleoc.: X= yellowish, Y and 3H2O Z=dark bro\vn and nearly opaque. 1.577 1.760 Cordylite...... Hex. Pyram..... <0001>perf...... Wax-yellow...... H=4.5 Sol. in HC1. B.b. decrepitates and be­ Ce2O8.3CO2.BaF2 G=4.31 comes brown. Pleoc.: &>= greenish yel­ low, e brownish yellow. Hex...... None...... Green-brown...... H= 6 to 6.5 Sol.inHCl. F=dif. strong. Borosilicate of Y and Ba. G=4.41 1.760 1.768 Trig...... { 0001 }perf . parting. H=9 Insol. in acid. Infus. Pleoc.: &>= green, A1203 G=4.0 «=blue, etc. Anom., 2V up to 58°...... do...... {000l}perf...... H= 5.5 to 6 Imperfectlv decpd. by HC1. Infus. but CaO.SnO2.B2O3 G=4.20 sinters. 1.570 1.788 <10ll}perf...... White...... H=4...... Sol. in hot acid. Infus. Data for mineral (Fe,Mg)O.CO 2 G=3.43 with percent, of FeCOs= 50, MgCO3= 50. Palmerite ...... Mic. hex. plates . . . Colorless, with G=3.33 Sol. in HNO8. Decpd. in boiling H2O. 3(K,Na)20.4Pb0.7SOs pearly luster. F=easy.

1 79 1 80 Decpd. by acid. Elongation of fib.+. FessOs.WOs.eHsiO fib. 1.55 1.80 Earthy...... Rose-red...... H=soft...... Sol. in acid. Infus. CoO.CO2+nH2O 1.80 {0001>mic...... Black...... H=3.5 Chlorite group. Gelat. F=4. Pleoc. 3(Fe,Mg)O.Fe2O3.2SiO2.3H2O hex. pyramids. G=3.34 marked: Dark reddish brown to nearly opaque. 1.761 1.815 Hex. Lamellar. . . {0001>perf...... Pale green, color­ H=3to4 F= dif . In section colorless. 2(Pb,Mg)6.SiO2.H2O less. G=4.72 1.S18 1.818 Trig...... {10ll}perf...... H=5 Sol. in acid. Infus ZnO.COa G=4.4 1.597 1.817 .....do...... do...... Pink...... H=4 Sol. in acid. Infus. Turns black on heat­ MnO.COa G=3.70 ing. Data for mineral composed of pure MnCOs. 1.715 1.820 Trig. Rhombs. { 0001 }dist...... Yellow H 3 Alunite group. Sol. in acid. F=4.5. KsO.3Fe2O8.4SOs.6H2O Tablets. G=3.2 Base divided into six biax. segments. 1.73 1.82 Trig.? Plates...... do...... do...... Sol. in HC1. 3FeijO8.4SO8.10H2O G= 2.5 to 2.7 1.605 1.826 Rhodochrosite...... Trig. Rhombs.... <1011}perf...... Pink...... H=4 Sol. in acid. Infus. Turns black on heat­ (Mn,Fe)O.CO2 G=3.74 ing. Data for mineral with percentages of MnCOa=79.3, FeCOa=19.9, CaCO3 =0.8. 1.596 1.830 Trig...... do...... H=4 Sol. in HC1. Infus. Data for mineral (Fe,Mg)O.C02 G=3.64 with percentages of FeCOa=73.2, MnCOs=.22, MgCO8=23.3, CaCOa=1.3. 1.750 1.832 {0001}dist...... H 3 Alunite group. Sol. in acid. F=4.5. Na2O.3FesO8.4SO8- 6H2O G=3.2 Faintly pleoc.: «=pale yellowish, e= colorless. 1.615 1.849 Trig...... <10ll}perf...... H 4 Sol. in acid. Infus. Data for mineral (Fe,Mn)O.COa G=3.80 with percentages of FeCO3=77.2, MnCOs=15.8, MgCC>3=6.6, CaCO3=0.4. 1.613 1.855 .....do...... do...... do...... H 4 Sol. in acid. Infus. Data for mineral with FeO.CO2 G=3.78 percentages of FeCO3= 90, MgCO3=5. CaCOs=5. B=0.04± 1.85 G 4.36 CuO.PbO.Fe,O3. 2SO8. 4H2O B=weak Trig...... Black...... H 4 Sol. in HC1. F=easy. Streak brown. 3MnO.As2Os G=4.23 Not pleochroic. 1.803 1.853 .....do...... do...... H 6.5 Insol. in acid. Infus. Pleoc. strong. MgO.2(Al,Fe)2O3, some TiO2 G=3.81 o>=dark brown, e= light yellow-brown. Alteration of pleonaste. 1.60 1.855 .....do...... {lOTl}perf...... H 3 to 4 Sol. in acid. Infus. Colorless in section. CoO.COs G=4.1 1.792 1.870 Orth.? Fib., tab. {001}perf...... H 1 to 2 Sol. in acid. F=3. Pleoc. in brownish 6CaO.4Fe8O3.3As2O8.9H2O(?) (001). G= 3.5 to 3.9 red. Abs.: &>>e. 1.633 1.875 Trig...... <1011}highlyperf.. H 4 Sol. in acid. Infus. Data for pure FeO.CO2 brown. G=3.89 FeCOE. 1.784 1.875 {10ll>...... Alunite group. Sol. in HC1. Pleoc.: PbO.3Feji08.4S03.6H2O Powder. G=3.63 w dark brownish red, e=pale golden bO yellow. O to TABLE 7. Data for the determination of the nonopaque minerals Continued. o Uniaxial negative group Continued. fcO

Hardness and e O) Mineral name and composition. System and habit. Cleavage. Color. specific gravity. Remarks.

1.815 1.898 Arseniosiderite ...... Orth. Pris...... Black; blood-red H=4.5 Variety mazapilite. Sol. in acid. F= 3CaO.2Fe2O3.2As2Os.6H2O(?) in splinters. G=3.57 2 to 3? Pleoc. : o>= dark reddish brown. = nearly colorless. B=low. 1.93 Gorki te {0001}easy...... Olive, yellow, etc. H=4 Alunite group. Sol. in HC1. Abnormal 2PbO.3Fe2O3.P2O6.2SO3.6H2O G=4.2± green interference colors. Base divided into six biax. segments. 3= mod. 1.96 Trig. Acute rhombs .....do...... Olive, yellow, H=4 Alunite group. Sol. in HC1. F-=3.5. or low. 2PbO.3Fe2O3.AssO6.2SOs.6H2O brown, black. G=4.1± Abnormal green interference colors. Base divided into six biax. segments. 1.82 2.01 Bismite...... Hex. Tablets.... <0001}perf...... White powder. .... Soft Sol. in HNO3. Bi2O3.3H2O(?) G=4.36 2.00 2.03 -{001}perf.,{101>perf H=2.5 Sol. in warm dilute HNO3. F=l. 5PbCl2.4CuO.6H2O G=4.85 Luster on cleavage pearly. 1.926 2.041 Cumengeite...... do...... {101}very good, .....do...... H=2.5 Sol', in warm dilute HNO3. F=l. In 4PbCl2.4CuO.5H2O {110}good. G=4.8 section it is purer blue than the bol&te and pseudobol&te with which it is in- tergrown. 2.03 2.05 Boleite...... Tetrag. Cubic.... {100}perf...... do...... H=2.5 Sol. in warm dilute HNO3. F=l. 9PbCl2.8CuO.3AgC1.9H2O G=5.08 Luster on cleavage pearl v. Trillings on (001) of three individuals form pseudo-cubic faces. Gelat. F=2. B=very 2.05 Eulytite...... Ps.isomet. Tetrah. <110>imperf...... H=4.5 Gelat. F=2. d low. 2Bi2O3.3SiO2 G=6.11 2.042 2.050 Hex. Pris...... {10lOX10ll}traces. Green, yellow, etc. H=4 Sol.inHNO3. F=1.5. Resinous. Pleoc.: 9PbO.3T2O6.PbCls G=7.0± &>=green, e= greenish-yellow. Biaxial. 2.05 2.07 Trig. Tab.{0001}. {0001}dist...... Gray, white...... H=3 Gelat. F=2.5. 3PbO.2SiO2 G=6.72 1.94 2.09 Soft Sol. in acids. F=1.5. The data given 3PbO.2CO2.H2O G=6.14 are for the artificial product. 1.94 2.13 Bismutosphaerite...... Fib. concretions, Yellow, green, H=3to3.5 Sol. in acid. F=1.5 Bi2O3.CO2 basal tablets. brown. G=7.3to7.4 2.118 2.135 {1011}imperf...... Yellow, brown, H=3.5 Sol. in HNO3. F=l. Biax. in sections. 9PbO.3As2O6.PbCl2 colorless, etc. G=7.1 2.04 2.15 Matlockite...... Tetrag...... {001 >perf...... Yellow, greenish, H=3 Sol. in warm dilute HNO3. F=l. Biax. PbO.PbCls etc. G=7.21 2.14 2.16 Bellite...... Bright crimson, H=2.5. F=easy. Faintly pleoc. in pale pink. PbO,CrsO3)As2O3, etc. coatings. Acic-c. yellow, orange. G=5.5 Abs.: w>e. 2.20 2.25 Yellow...... H=3 Between vanadinite and mimetite. 9PbO.3(As,V)2O6.PbCl2 G=7 Decpd. by HCI. F=1.5. 2.10 2.26± {001 >perf...... Yellowish black. . . H=6 Zinc hausmannite. Sol. in HCI giving F 2Zn 0 .2Mn2O3.H2O G=4.55 Cl gas. Infus. Pleoc. faint: «=red- fei brown, «= nearly opaque. CO

2.182 2.269 Tetrag. Pyramidal {OOlXlH}imperf.. Green,gray, brown , H=3 Isomor. with scheelite. Decpd. by PbO.WOs etc. HN03. F=2. 6 rppf-fwspr Black...... H= 5 to 5.5 Sol. in HCI. F=2. StreaS chestnut- o PbOg G=8.5 brown. Nearly opaque. Basal sec­ tion shows six biax. segments. H H 1.95 2.31 Trig. Rhombs... {I0il}perf...... do...... H=6 Slowly sol. in HCI. Infus. Pleoc. faint (Mg,Fe)O.Ti02 G=3.9S in red-brown or purple. Abs.: oj>e. 3 {001}nearly perf... Yellow, green. .... H=2.5 to 3 Heliophyllite. Sol.inHNO3- F=1.5(?). § 4PbO.ASj!03.2PbCl2 (001). Crusts. G=6.9to7.1 In part biax. > iH i 2.14 2.34± {00l}perf...... Black...... H=6 Zinc hausmannite. Sol.inHClgivingCl 0 ZnO.MnsO8 G = 4.85 gas. Infus. Red-brownin section and faintly pleoc.: &>£. 2.304!,} 2.402U Wulfenite...... Tetrag. Tab...... {Ill \perf., {001} Colorless, yellow, H=3 Decpd. by HCI. F=2. PbO.MoOs {115}lessso. orange, greenish. G=6.9 llh, 2.46Li >{001}nearly perf... Brownish black . . . H=5to5.5 Sol. in HCI with evolution of Cl. Infus. Mn3O< G = 4. 72 to 4.^6 In section dark reddish brown and fcO nonplecc. o CO 204 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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Hardness Mineral name and 2V Optical orienta­ System and a Cleavage. Color. and specific Remarks. T 0 composition. Dispersion. tion. habit. gravity.

B-weak 1.364 43°...... X-6...... <001>perf...... White, red­ H=2.5 Sol. in H2SO4. F=2. Tw. 3NaF.AlF3 p dish, brown­ G=3.0 <110>, lamellar. Disp. good. ish. 76°...... X-6...... {OOl^dist...... White...... -- H-3 Alteration of cryolite. NaF.CaF2.AlF8.H2O p. Disp. strong. 1.452 1 44 Orth. Woolly...... do...... -- G-2.00 (Ca.K2,Na2)O. F= easy. Al2O3.6SiO2.6H2O? 1.439 1.469 36°...... Z-b...... H-2 Sol. in H3O. F=l. Sec- NajO.(NH4)sO. p>v rather YAc=30°. G=1.574 tion{010>shows two sets P2O5.9H2O strong. Disp. strong. of polv. tw. lamellae at about 90°. 1.447 1.459 Taylorite...... 36°...... do...... H=2 Sol.inH2O. F=1.5(?). 5K2O.(NH4)2O.6SO3 P>V rather strong. 1.45 65°±...... Z-b...... <010>perf...... White...... H=5 Zeolite group. Decpd. by (Sr,Ba,Ca)O.Al2O3. P>U weak. XAC=22°. <100>. G=2.45 acids. F=3. 6SiO2.5H2O 1.461 48°...... Y-6...... <201}perf...... do...... H=2.5 Sol.inH2O. F=2. MgO.KjO.2SO3. p>i> mod. XAC= -1°. Crusts. G=2.1 6H2O 1.459 1.470 1.461 Aluminite...... Large...... Elong...... Mon. Fib...... do...... H= 1 to 2 Insol. in H2O. Sol. in acid. A12O3.SO3.9H2O Earthy. G=1.66 Infus. 1.465 .....do...... X-6...... Mon...... {010>perf...... H=3to4 Zeolite group. Partly (Ca,Nas,Ks)O.Al2Os. Z AC- 73.5°. Tab.{010>. etc. O=2.15 decpd. by acid. F= 4 to 5 10SiO2.6§H2O Fib. c. ' with intumescence. 1.469 1.479 50°...... Y-6...... Mon...... White...... H-2 Sol. inH2O. F=l. (NH4)2O.MgO. p>u slight. . Z near a. . G= 1.68 to to 2SO3.6HS0 1.72 o fcO TABLE 7. Data for the determination of the nonopaque minerals Continued. o Biaxial positive groap Continued.

Hardness 2V Optical orienta­ System and a Mineral name and Cleavage. Color. and specific Remarks. T & composition. Dispersion. tion. habit. gravity.

1.469 1.473 1.47 X-6...... Orth...... Indistinct..... Colorless ...... H=6.5 Sol. in boiling NasCOs- Si02 Z=c. Ps. Hex. C,=2.30 Infus. Tab.<0001}. 1.51 1.47 Opt. pi. J.< 010} {001>perf...... do...... H=2.5 Sol. in acid. Tnfus. Alters MgO.CO2.5H2O G=1.73 on exposure to air to nesquehonite.

1.466 1 494 1. 475 70°...... Z-a...... Orth...... White, red­ H=2.7 Deliquescent. F= 1 to 1.5. KCl.MgClz.fiHjO Pu weak. Y=c. G = 2.69 to 2. 1.474 69°...... X-6...... White...... H=1.5 Keramohalite. Sol.inH2O. A12O3.3SO3.16H2O ZAc=42°. Tab.<010>. G= 1.64 to Infus. Fib. c. 1.67 1.471 86°...... Y-ft...... <00l>oerf...... H=2 Sol. in H2O. Tastes astrin­ FeO.SO3.7H20 p>« weak. ZAC= 6i°. <110}good. fresh), yel­ G = 1.90 gent. F=easy. Alters on Disp. low. exposure to dry air. 1.478 1.482 1 479 50°...... Y=6...... Orth...... <100}perf..... White...... n=3to3J Insol. in HC1. F=3 to 3J. 2RO.Al2O3.5SiO2 Z=c. Blades { 100 >. G=2.15 R=Mg :Na 2 : Hs Elong. c. =1:1:1 1 472 1 487 1.479 Y-ft...... <001}easy...... Blue...... H-2to3 Sol. in H2O. F=3 to 4. (Fe,Cu)O.S03.7H20 Disp. weak. X near c. 0=1.9 Alters readily by de­ hydration. («) (») («) Y-b...... {001}imperf...... do...... H=2.5 Sol. in H2O. Fus. Color­ CuO.SO3.7H2O X near c. Fib. c. 0=1.94 less in section. Decom­ poses to chalcanthite on exposure to dry air.

1.475 1.480 White...... Sol. in H2O. F=easy. k2O.2SO3.HsO fib. 1.475 1.488 1.480 Dietrichite...... do...... X _ j, Mon. Fib. c...... do...... H=2 Sol. inHjO. Infus. (Zn,Fe,Mn)O.Al2O8. ZAc=29°±. 4SO3.22H2O B=weak 1.480 Oct...... {lll}dist...... do...... H=5 Zeolite group. Decpd. by N^O.CaO^A^Oa. ' G=1.92 acid. F=3. Uniax.+ . 10SiO2.20H2O In eight segments from loss of H2O.

B=0.001 1.481 Ps. trig...... {1010} easy.... Colorless, yel- H=4 roup. to 0.009 (Na2,Ca)O.Al2O3. 1 o wi sh, G=2.17 acid. F=3.?=3. Tw. axis c. 4SiO2.6H2O greenish. B= 0.003 1.48 70°...... Y-6...... {001} {010} H=4 Zeolitegroup. Gelat. F=3. (K2.Ca)O.Al203. P

1.480 1.493 1.482 63°...... X-a...... Orth...... {110}perf. .... White...... H=5 Zeolitegroup. Gelat. F=2. Na2O.Al2O3.3SiO2. p

1.484 1.496 1.487 60°...... H-l Sol. in HjO. Fus. Poly, Na2O.Al2Os.4SO3. Disp. slight. YAc=30°±. Laths {100}. G=2.03 tw. 12H2O Fib. c. 1.473 1.511 1.490 85°...... Y-a...... Orth...... do...... H=3 Insol. in acid. Infus. A1F8.H2O p < u rather Z=c. G=2.17 strong. B= mod. 1.491 49° Y-6...... Isomor. with picromerite. K2O.CuO.2SO3. XAC=4°. Crusts. Sol. inHjO. F=l(?).

1.494 1.497 1.495 67°...... X-6...... {010X001 }good G=2.67 Sol. in HSO. Artificial. P>U mod. Z=c. 1.495 1.504 1.496 37°...... Z-b...... do...... <001}perf..... H=2 Sol. in acids. F=3. (NH4)2O.2MgO. p

Mineral name and 2V Optical orienta­ System and Hardness a 1 ft Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.498 1.505 1 499 34°±...... Z=&...... {010} per!...... White...... H-4 CaO.Al2O3.6SiO2. p>v. YAc=6°±. Tab. {010}. G=2.2 Decpd. by HC1. F=2. 5H2O Opt. pi. sometimes .//{010}. 1.498 1.503 1.50 Wellsite...... 39°±...... Z=&...... H-4to4.5 (Ba,Ca,K2)O.Al2O3. XAc=-52°. G=2.28tO acid. F=3. Complex 3SiO2.3H2O 2.37 tw. 1 499 1.538 42°...... X=a...... 2CaO.UOj.4CO2. p>u perc. Crusts. 10H2O 1.501 1.510 1.503 63°...... Y=6...... {211>dist. .... H-4. 5 CaF2.2Al(F,OH)3. p>u strong. ZAC= 50°. Tab. {010}. G=2.88 H2O 1.497 1.525 1.503 54°±...... X=a...... Orth...... '.. {010}perf. .... White...... H-5 (Na2.Ca)O.Al2O3. p>v strong. 2=6. Fib. c. La­ {100} good. G=2.36 2Si02.2*H20 mellar {010}. 1.491 1.520 1.504 Ulexite...... Mod...... X=&...... Mon ...... do...... H=l Sol. in acids. Slightly sol. Na2O.2CaO.5B2O3. YAc=23° Fib.c. "Cot­ G=1.65 in H2O. F=l with intu­ 16H2O toO. ton balls." mescence. 1.503 1.508 1.505 43°...... Z=&...... {010} easy...... do...... H-4.5 (K2,Ba)O.Al203. XAc=60°. Pris. o. {001} less so. G=2.5 HC1. F=3.5 Tw. pi. 5SiO2.5H2O {001 } cruciform. 1.505 1.506 1.505 Trie...... {110}{110}perf. H-5 Na2O.2CaO.3Al3O3. P>v strong. YAc=5°±. Needles c. G=2.27 F=easy. Tw. pi. {100} 9SiO2.8H2O common. 2V changes rap­ idly with temp. B=0.002 1.5 Trie {110}{110}perf. H-5 2CaO.Na2O.3Al203. Fib. c. G=2.22 X and Y are // to diago­ 9SiO2.8H2O nals of rhombs in cross sections. 1.495 1.528 1.507 79°...... X-&...... H-1.5 MgO.CO2.6H2O p>v. YAc=94°. Fib. G= 1.591 1.504 1.545 1.508 JQ' Z-c?...... Trie H-6to7 2Na2O.Al2O3.6SiO2. lamellar tw. G=2.50 H50 0.001 1. 50S Z=a...... Orth...... Colorless ...... H=6 Decpd. by acid. InfuS. K2O.Al208.4Si02 Ps. isomet. G=2.5 1.504 1.575 1.510 33°...... X-o...... Orth...... None ...... do...... H=3 Effervesces in acid. Slightly CaO.Na2O.2CO2. Z=&. Elong. c. G=2.35 sol. in H2O. F=1.5. 2H2O Tab.<010>. 0.003 1.51 70°...... X-&...... { 001} {010 > ra­ .....do...... H=4 Zeolite group. Gelat. F=3. (K2.Ca)O.Al2O3. p Red, green, H=6 Insol. in acid. F=5. Li3O.Al2O8.8SiO2 pperf...... do...... H=3 Sol. in HNO3. 2MgO.P2O6.7H2O P. {OOUimperf. G = 2.10 1.516 1.533 1.518 48"...... Z-c...... Orth...... {001>perf..... H=1.5 Sol. in acid. Infus. !Lath- 2Al203.S'08.10Hi10 p>u perc. X=elong. Scales { 001 >. G=2.33 shaped cleavage pieces. 1.515 1.525 1.518 Trie...... {100} dist...... do...... H=3.5 Sol. in acid. F=3. 2CaO-.P2O6.H2O from {100}. Rhomb. G=2.75 1.509 1.561 1.52 60°±...... X-6...... Mon. Tab. {001>perf...... do...... Soft. Cleaved rhombs resemble (NH4)20.5B208. Y near a. <100} with hexagonal plates. 5H20 Z/\c= large . rhombic outline and angle 66°. 1.510 1.543 1.520 71°...... Y=6...... Mon...... {010V...... do...... H=lto2 Sol. in acid. Fus. 3MgO.P2O5.8H2O p« perc. XAc=37J°. Tab. {010}. G=2.32 Tw. and comp. pi. {100}. Disp. strong. 1.521 1.533 1.523 coo Z-o...... Orth...... {001} dist...... H=2 Sol. in H2O. Tastes pun­ fcO (N£f4)2O.S03 P>V feeble. X=c. Elong. c. 1 o w i s' h , G=1.76 gent and bitter. 1 = 1. O greenish. Volatile. Tw.pl. {110}. CO TABLE 7. Data for the determination of the nonopaque minerals Continued. to Biaxial positive group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a 7 ft Cleavage. Color. and specific Remarks. 0 composition. Dispersion. tion. habit. gravity. 02§ o 1.518 1.588 1.523 33°±...... Z-c...... Orth...... {001}...... White...... H-l o Cj8H78 Pu strong. Y=&. Fib. c. s t r a w-yel- G= 2.15 to X= colorless, Y= very pale 7H20 low. 2.36 amber-yellow, "Z=pale amber-yellow. 1.508 1.550 1.526 81°...... Y-6...... {100}{001}perf. White...... H=4.5 Sol. in acid. F=l. KjCMMgO.llBsOs. Disp. not ZAc=65°. G=2.13 18H2O perc. 1.507 1.573 1.529 73°±...... 001 perf...... H=2.5 Sol. in acid. F=4.5 to 5. 2FesOs.5SOs.16H2O P>I> rather angle. bic tablet ron-yellow. G=2.10 Pleoc.: X = yellowish strong. {001} with green. Y=very pale yel­ angle 77£°. low, Z= sulphur-yellow. 1.525 1.536 1.529 Albite...... 74°...... On {010} X' A < 010X001} perf. H-6 Na2O.Al2O3.6SiO2 pu rather brown. G=2.12 Pleoc.: X and Y= color­ 13H20 strong. less, Z= rather deep or­ ange-yellow or orangc- 1.530 1.545 1.533 50°...... -. Y=p. long Orth...... One perf...... Colorless ...... H=5. . Decpd. by acid. (CaNa2)O.2Al2O3. XJL perf. Fib. 3Si02.4H20 cleav. Needles. 1.533 1.575 1.534 Orth. Fib. c... PaleyeUow... H=2 Sol. in H2O. F=4.5 to 5. Fe203.2S03.10H20 G=1.86 Pleoc.: X and Y nearly colorless, Z=pale yellow.

1.517 1.565 1.534 {100X010}perf. White...... H=2 Sol. in acid. CaO.MgO.3B2O3. p< v perc. XAc=31°. Fib. c. G=2.0 F=2. 6H2O H iCo 1.525 1.552 1.534 72°...... Z=c...... Orth. Radiat­ { 101} {010} White, yellow, H=3 to 4 Sol. in HC1. Infus. 3A12O3.2P2O5. p>v small. X=6. ing fib . c. rather perf. green. G=2.3 to 13(H«O,2HF) 2.5 i B=very 1.535 Bromcarnallite...... 87°...... X=a...... Orth.Ps.tetrag: None...... H=2 Tw.{110}. strong. MgBr2.KBr.6H2O Disp. slight. Z=6. 0 1.523 1.586 1.535 57°...... Y-6...... Mon...... White...... H=3.5 Slowly sol. in H2O . F= 2 to 3. o MgO.SO3.H2O P>U mod. ZAc=76.5. G=2.57 B Disp.dist. Illljgood. H 1.530 1.595 1.543 Mod...... X=c...... Orth. Rhom­ {001}perf...... Yellow, red­ H=2.5 Sol. in acid. F=4.5 to 5. W 2Fe2O3.5SO3.18H2O p>v rather Z. bisects bic tablets dish, violet. G=2.10 Pleoc.: X= yellowish g strong. acute angle. {001}, 77£°. green. Y= very pale yel­ Elong. a. low, Z= sulphur-yellow. g'§ B-0.013± 1.54± Z=c...... Orth. Fib.c.. {010}...... Green, brown, H=4 Serpentine. Decpd. by acids. 3MgO.2SiO2.2H2O yellow. G=2.5 F=6. Pleoc. faint. Abs.: Z>Y>X. 0

1.541 1.554 1.545 Z=c...... do...... White...... H=3 Sol. inHCl. F= 2 to a black 2CMn,Zn,Mg)O. G=3.12 mass. o B2O3.H2O 1.539 1.551 1.545 86°...... Mon ...... {010}perf...... do...... H=2 Sol. in dilute acids. F=3. g 2CaO.P2O6.5H2O XuAC=9.2°. Flattened{010} {301}perf. G=2.25± 52j XTiAc=11.2e. Elong. c. H 1.545 1.551 1.546 30°...... Y=6...... Mon...... {001}perf...... '....do...... H=6 Insol. in acid. F=2.5 to 3. > Na2O.2GlO.6SiOs. p>« dLst. ZAc=-58}°. Tab. {001}. {551}imperf. G=2.55 Tw. pi. {001} lamellar al­ F H2O ways present. Cft 1.541 1.564 1.547 Voglite Tric.f ?)...... Emerald-green Soft. Poly. tw. lamellae // plates. Hvdrous carbonate p

Mineral name and 2V Optical orienta­ System and Hardness a T ft Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.530 1.592 1.550 69°...... X=6...... Mon...... <010> perf., H=2.5 Sol. in H2O. F=1.5 to 5. 2Fe2O3.5SO3.18±H2O P>U rather Tab. <010>. <100}lessso- dish violet. G=2.21 Pleoc.: X=yellowish strong. Fib. green, Y=very pale yel­ low, Z= sulphur-yellow. 1.550 1.557 1.553 Andesine...... 88°...... On{010>X'A Trie...... perf. Colorless, etc . . H=6 Feldspar group. AbeoAnw- Ab3An2 {001>=8°. G= 2.676 Insol. in acid. F=4 to 4.5. On{001>X'A Polv. tw.{010} almost uni­ <010}=2°. versal. Other laws com­ mon. B-0.016 1.554 Grothine...... Medium...... Y-c...... Orth ...... G=3.09 Easily decomposed by Silicate of Ca, A l,Fe. p. H2SO4. Infus. 1.533 1.635 1.555 Rhomboclase...... Small...... <001>...... do...... Fe2O3.4SO3.9H2O plates. 1.555± Soumansite...... Oto70°...... Z=c...... Ps. tetrag. .... H=4.5 Sol. in acid. Nearly infus. Phosphate of Al and Oct. G=2.87 Basal section divides into Na with H2O and F. four segments. 1.491 1.650 1.555 Whewellite...... 84°...... X-b...... {OOIHOIO>..... H=2.£ Sol. in acid. Infus. Tw. CaO.C2O3.H2O P heart-shaped. 1.551 1.582 1.558 55°...... X-a...... Orth...... H=4 Sol. in HC1 after ignition. A1208.P206.4H20 Pperf. H=--6 Feldspar group. Feldspar. P>V slight. o=l° to 5°. AbgAnioCg. On {010} X' A a=2°toll°. Z=nearx<001>. Y=neari{001>. 1.494 1.692 1.561 Yellow H=2 Sol. in acids. Pleoc.: X= FeO.C2Os.2H2O Z=c. { 100X610 > G=2.28 very pale yellowish green, less so. Y=pale greenish yellow, '/ inl-pncp vAllnw ' 1.559 1.568 1.563 79°...... On {010} X'A Trie...... {001X010}perf. H=6 Feldspar group, Ahv dist. or ZAc=-25°± Hex. tab. ish, etc. G=2.35± p 4SiO2.4JH2O 1 44°. {011}penet. simulating tet- rag. or orth. forms. 1.555 1.585 1.57 Fib. Powder...... do...... Sol. in acid. Y,G1,C08 1.569 1.582 1.570 "Wasnerite...... 26±...... ZAc=214°.....Y=b. " Mon...... { 100X110} im- Colorless, yel­ H=5 Sol. in acids. F=4. 3MgO.P3O5.MgFa p>»> perc. perr. low, flesh- G=3.0 Disp. weak. red.greenish. 1.563 1.596 1.571 Hoernesite...... 60...... H=l Sol. in acid. F=2to3? 3MgO.As2O5.8H2O ZAc=31°±. Tab. {010}, G=2.60 elong. c. 1.576 1.579 1.576 0±...... ZAc=0±...... Mon ...... {001}mic. ... Green...... H=2.5 Decpd. by H2SO4. F=dif. 5(Mg,Fe)O.AlaO3. p

Mineral name and 2V Optical orienta System and Hardness o a T ft composition. Dispersion. tion. habit. Cleavage. Color. and specific Remarks. w gravity. o cc o B- 0.014 1.6± 2E=25°to30°. Z sensibly j_ {0001 >mic.... G=2.89 Decpd. by H2SO4. F=easy. o 2Li2O.7Al2O3.2B2O3. cleav. Basal section divides into 6SiO2.12H2O six segments with the opt. pi. parallel to the hex. edge. 1.680 1.589 1.580 Oto36°...... Mon. Plates.. H=2.5 Chlorite group. Decpd. by 5(Mg,Fe)O.Al2O8. p. G=2.7 for mineral with 1.8 per 2(Cr,Al)gO8 Fib. cent Cr2O3 and little Fe. bj o 1.583 1.593 1.583 Eakleite...... Very small.... Orth. (?)Fib.. Perfect along Colorless to H=6.5 Easily sol. in acid with sepa­ b{ 5CaO.5SiO2.H2O fib. pink. G=2.70 ration of flaky silica. F=2.5. 8 1.578 1.591 1.585 Large ...... Y=c...... Orth...... {HO^perf. a t G=2.86 Amphibole group . Data on MgO.SiO2 pure artificial mineral. 1.585 1.596 1.586 0 to 90°...... Y-6...... Mon. Plates {001}perf...... H=2.5 Chlorite group . Decpd. 5(Mg,Fe)O.Al2O3. P and fib. G=2.7 by hot conct. H2SO4. 3SiO2.4H2O F=5 to 5.5. Pleoc.: X and Y green to brown, Z yellow, etc. Abs.: X>Y>Z. B low. 1.587 OtolO"...... XAC=O...... Greenish-white H=1.5 Chlorite group. Insol. in 7MgO.8Al2O3.10SiO2. G=2.68 acid. Infus. 14H2O 1.584 1.594 1.589 87°...... Y-b...... {OOlVperf...... H=6 Barium feldspar. Sol. in BaO.Al2O3.2SiO2 ZA<*=28°. {010}good. G=3.37 HC1. Infus. TABLES FOR DETERMINATION OF MINERALS. 215 -. :*w « SI ft fl 1? 6X)C 7 I £§'53^ it? i-g>.H '3k §1 ^^cu*3 >f ^o g TJ « It II-,,ife « Is

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s-* soo @t~ TABLE 7. Data for the determination of the nonopaque minerals Continued. toI ' Biaxial positive group Continued. 05 g Hardness . h-1 Mineral name and 2V Optical orienta­ System and O a 7 & composition. Dispersion. tion. habit. Cleavage. Color. and specific Remarks. gravity. O Cfi 0 1.579 1.633 1.603 *7Q° i X-6...... {010>perf...... H-2 Sol.inHCl. F-1.5. Color­ O 3FeO.P2O5.8H2O Pmic...... Soft 2FeO.2MgO. P perc. Plates{001>. 0=2.9 hot conct. H2SO!. F=5 Al2Os.2SiO2.2H2O. Vermicular. to 5.5. Pleoc.: X and Y= nearly colorless, Z= greenish or brownish. B=0.02 1.606 Y-6 and bi­ Mon(?)...... 5CaO.2PaO6.ljHaO sects obtuse Rhombic G=2.89 angle of tablets rhombs. (65°). Z emerges from- plates. 1.595 1.634 1.606 Pectolite...... 60°...... Z=ft...... Mon. Acic. b.. <100K001}perf...... do...... H=4.5to5 Partly decpd. by HCL F=2. NauO.4CaO.6SiO-!. P>V slight. YAO= small. G=2.74 to <£> H20. 2.88 d 1.605 1.613 1.607 <001}mic...... Soft ll(Fe.Mg)O.4Al2O8. P{010>.... H-3.5 2CaO.FeO.P2O5. P>U perc. Radiating. white. G=2.81 4H2O TABLES FOR DETERMINATION OF MINERALS. 217

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Hardness Mineral name and 2V Optical orienta­ System and a ft Cleavage. Color. and specific Remarks. T composition. Dispersion. tion. habit. gravity.

1.621 1-623 Ext. on {010} Tric.(?)...... Powder . . . Sol. in acid. Plates lying on CaO.8UO3.2SO3. p 1.631 1.624 51°...... _ . Orth...... {001}perf...... H=3.5 Insol. in acids. F=3. SrO.SOg p nearly G=3.96 so,{010>less so. 1.624 68°±...... X-6...... Orth...... H=6 Gelat. Infus. Pleoc.: X= 6MgO.3SiO2. P>V weak. Z=c. Tab. {010}. low, brown. G=3.1 golden yellow, Y and Z= Mg(F,OH)2 nearly colorless. Poly. tw.{001}. 1.615 1.665 1.625 Tric.(?)...... White powder. H=3 Sol.inHCl. F=dif. 2Fe2Os.P2Os.2SO3. p>u rather j. plates, Z Minute six- G=2.1 2H2O strong. to elong. 16°. sided tab­ lets. 1.614 1.637 1.625 Ext.{ 100} {010>perf...... Colorless ...... H= 3.5 to 4 Sol. in HC1. F=easy. Tw. 3ZnO.P2O,.4H2O pv weak. Z=c. Elong. c. G=2.9 Luster on {001} pearly. HSO B-0.02± 1.63± Imperf...... Yellow...... H=5 Altered homilite. Gelat. 3(Ca.Fe)O.B2O3. r- weak. Z=a. {001}. {010}imperf. G=4.5 {110} lamellar. 1.64 1.66 1.64 Small...... Colorless...... H=3 Gelat. F=3. W 7CaO.2(Ca,Pb)0. G=3.43 5SiO2.2SO2.5HzO cc 1.640 1.657 1.640 Sarcolite...... Small...... Ps.Aetrag..... Reddish white, H=6 Gelat. F=2.5 to 3(?). 3(Ca,Na2)O.Al2O3. p>v strong. Cubo-oct. flesh-red. G=2.7± Anom. biax. 3Si02 0 1.633 1.657 1. 612 X-o...... Orth...... {110} perf. at Gray, brown, H=6 Amphibole group. Insol. O (Mg,Te)O.SiOs pv strong. Z=c. and n ee- G=3.23 for artificial mineral. dles // c. g 1.636 1.654 1.644 Fairfieldite...... Ext. on{100}- Trie. Pris., {010} highly Nearly color­ H=3.5 Sol. in acids. F=4. 2CaO.MnO.P2Os. 40° to c, on foliated, fib. perf., {100} less. Luster G=3.1 2HSO {010}= 10°. good. on {010} t i pearly. O B=0.01 80°...... Nut-brown to H=5.5 Sol.inHCl. F easy. Tw. 2CaO. Tab.{010}. brownish red G= 3.35 to pi. {001} contact, {100} O 3(Al,Fe,Mn,Ce)2Os. 3.70 lamellar. Commonly al­ 4Si02.3HjO tered; optical properties vary and finally the min­ eral becomes isotropic. 1 1 H 1.646 1.65S 1.649 XAC=2"±.... Mon.(?)...... Reddish brown H=4 Near johnstrupite. Sol. in Contains Ti,Si,Ce,Ca, p>w strong. Elong. c. G=3.0 HC1. F=3. Na, Zi,O, etc. Ul B=0.02± 1.65± Yellow...... H=5 Alteration of homilite. 3(Ca,FejO.B2Oi P^U very G=3.4 Gelat. F=2. SiO2+raH2O(?) strong.

IbO 1 CO TABLE 7. Data for the determination of the nonopaque -minerals Continued. fcO 60 Biaxial positive group Continued. o

Mineral name and 2V Optical orienta­ System and Hardness a 7 ft Cleavage. Color. and snecific Remarks. composition. Dispersion. tion. habit. gravity.

B-0.03 1.65-t Z-c...... Orth. Fib. c.. H 4.5 (Al,Fe)!08.PsOs. P>V strong. G=2.6± 4H2 0 1.635 So8 ...... X b IT 7 2MgO.SiO2 pv. Y=6. 87°. G=3.18 pure artificial mineral. Tnsol.inacid. F=6. 2V, index, and B increase with FeO content. 1.680 1.653 Trie 3(Ca,Fe)O.P2O5. Slight. 20° to c. Tab.{100}. brownish. G=3 21H2O B=0.029 1.654 72°...... Y=6...... {110} dist. at H-6.5 Na2O.Al2O3.4SiO2 pYandZ. 1.651 1.660 1.654 Cllnoenstatite ...... 54°...... X=6...... {110} perf..... G-3.28 £> MgO.SiC-2 Slight. ZAc=22°. acid. Infus. Data on arti­ ficial mineral. Poly. t\v {100} characteristic. 1.655 1.662 1.655 Small...... Z-c...... Matted. Fib.c H- 2 to 2.5 UOs,CuO.CaO.SO8, apple-green. terlcrencecolors. Faintly H2O colored and pleoc.: X and Y very pale yellowish green, Z=paie-greenish yellow. 1.652 1.671 1.655 50°...... Y-ft...... {010}perf...... H-7.5 2GlO.AhO3.2SiO3 . p>v. XAc=42.3°. {100} {001} blue. G = 3.l H20 poor. 1.649 1.714 1.656 076 Y-6...... do...... {001}perf...... H-4.5 Sol. in H2O slowly. F= NasO.4CuO.3SO8. P strong. ZAc=-12°. G=2.33 easy. Dispersion of bisec­ 3H2O Disp. strong. trices strong. Z Ac for red is greater than for blue. IJ=0.03 1.656- 80° ± XAc=27°±... {001}perf...... H-6 Humite group. Gelat. Infus. 4MgO.2SiO 2. p>v weak. Y=6. O=3.1 Tw.pl.<001}poly. Pleoc.: Mg(F,OH)2 Disp. , X= Honey-colored.golden, or brown; Y and Z nearly colorless. 1.651 1.683 1.656 41° ...... Orth. Oct.... Onedist...... Pink, violet, H= 3 to 3.5 Sol. in acid. F=2.5to3. 3MnO.P205 .3H2O p>v strong. red-brown. G=3.10

1.640 1.695 1.658 Veszelyite...... 71° ...... Mon. or trie... Greenish blue . H= 3.5 to 4 Fus. Pale greenish blue and 7(Zn,Cu)O.(P,As)2O6. />< v very Incrustations. G=3.53 nonpleoc. in section. 9H2O strong. 1.655 1.670 1.66 Salmonsite...... Very large..... Z// fibers...... Orth. Massive Twoat90°dist. Yellowish ..... H=4 Pleoc.: X= nearly colorless, Fe2O3.9MnO.4P2O6. pI> strong. ZA«=42°. {010>ponr. G=3.79. on mineral with 1.7 per cent FeO. Abs.: X>Y^ Z. 1.659 1.680 1.660 20°...... X-6...... {lOOVperf...... White...... H-6 Insol. in acid. Infus. May Al2O8.SiO2 p>u strong. Z=c. G=3.23. be pleoc. 1.626 1.699 1.661 90°±...... X-&...... <010>highlv Crimson to H= 1.5 to 2.5 Sol.in HC1. F= 2. Strongly 3CoO.ASisO5.8H2O P elong. perf. gray. G=2.95. pleoc.: X=pale pinkish, c. Y=very pale violet, Z= red. Colors vary. 1.645 l.CSS 1.661 77°...... Z 6 {010}dist...... "White, gray- 1^=6.5 F=dif. Tw. 2Na2O.BaO.2TiO2. p>u rather YAc=3°. blue. G=3.05. 10SiO2 strong. W 1.640 1.680 1.661 Forsterite...... 90°±...... X=6...... Orth. Equant...... do...... Colorless, etc . . H=7 Olivine group. Gelat. Infus. f> 2MgO.SiO2 P 1.658 1.671 1-662 Med...... X-6...... Mon. Tab. . . . {001}perf...... H= 3.5 to 4 Sol. in acids. F=2.5 to 3. SCMn-Fe-Na^O. p>u strong. Y near c..... Foliated{001> G=3.34 Pleoc. in green. Abs. X> P2O5.§H2O Y»Z. 1.629 1.727 1.662 73°...... Mon.?...... {010}perf...... H- 2 to 2.5 F=2to3(?). 3NiO.6CuO.SOa. p<« strong. Y=6. Oblong rhom­ G = 2.0 to 2As2O6.7H2O bic tablets 2.5 {010}. Fib. ' to bO tc TABLE 7. Data for the determination of the nonopaque minerals Continued. tc fcC Biaxial positive group Continued.

Hardness y ' Mineral name and 2V Optical orienta­ System and O v very G=3.38 njI < 2SiO2+nH2O(?) strong. O 1.661 1.673 1.666 Johnstrupite ...... 70°...... XAc=2°...... Mon...... <100}dist...... Brownish green H=4 Sol. in HC1. F=3. Poly. Silicate of Ce, Ca, P>V strong. Y=6. G=3.29 tw.^lOO>. In section color­ § Na, etc., contain­ less. ing FandTi. 3» 1.660 1.676 1.666 58°±...... Y=6...... <110>perf.at 88° White, yellow, H=6.5 Pvroxene group. Insol. in g Li2O.Al2O3.4SiO2 pparting etc. >Y>Z. rare. 1.662 1.673 1.667 Boracite...... Very large..... Orth...... Y>X. Nearly color­ 16NaP less in section. 1.665 1.674 1.669 Enstatite...... 80°...... X=o...... Orth. Pris. c. <110V perf. at H=5.5 Pyroxene group. Data for (Mg,Fe)O.SiO3 p>i> weak. Z=6. 88*. G=3.2 mineral with 5 per cent FeO. Insol. in HC1. F=6. 2V, index, and B increase with iron. B-0.04 1.670 2K=80°...... Z=6...... H=6 Humite group. Gelat. 2MgO.SiO2. XAa=47°. G=3.1 Infus. Poly. tw. {001 } Mg(F,OH)j common. B=-0.014 1.67 18°...... Z-6...... Parallel to H=7.5 2(Al.Fe)2O3. YAcleav.28°. length perf. O=3.23 3(Ca,Mg)O.4SiOz. 2H2O 1.6o8 1.690 1.670 76°...... Z-6...... Yellow to H=6 Humite group. Gelat. 8MgO.4SiOz. p>v weak. XAC=9°±- reddish O=3.1 Infus. Pleoc.: X= yellow, Mg(F,OH)a Disp.perc. brown. Y and Z= nearly color­ less. Poly. tw.{001}. TABLES FOR DETERMINATION OF MINERALS. 22$

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S;l rt '*" O i'S'S Iggf st s£ .0 § 'S ba s5 .is II w"flO ^!^ R C 1.709 1.687 Aegirite-augite ...... 60°...... Y=»6...... Mon ...... {110>perf.at88° Green, yellow . H=5to6.. Pyroxene. Pleoc.: X=-grass- Between augite and p>v. XAC=6° to Pris. c. 0=3.5 green, Y= light green, aegirite. 38°. Z= yellow to brownish. 1.679 1.710 6.5°...... Y=6...... do...... <110>pcr!.at 87" H=5to6.. Pyroxene between diopside NajO.2FeO. plithiophilite. ., LijO.2(Fe,Mn)0. Disp. very Elong. c. {OlO>dist. bluish. Data for mineral with g Pj05 strong. 26.58 per cent FeO. Sol. U in acid. F=2. With in- S creases of FeO (3 increases & and X=o. B decreases Of and passes through 0 and mineral becomes opt. . £^ 1.710 72"± ...... Mon...... Brown, green, H=4.5.... Pyroxene group. Data for ^ (Mn,Zn,Fe,Ca)O. p>v perc. Pris. black. G=3.39 mineral with percentages M SiOa of MnO=7.4, ZnO=3.3. S CaO= 23.7, MgO= 12.6. In- H sol. in acid. F=dif. H W 1.711 1-691 13° to 67°...... Y=6...... <110>perf.at8S° (Mg,Fe,Ca)O.SiOj ZAC=46°±. Pris. c. acid. Infus. Pleoc.faint: 1-1 X= yellowish green, Y= !^ brownish red, Z= green- J> ish white. H B=0.005 1 693 Ext. large. .... Mon.?...... {100}imperf ... Green, brown, H=2.5 .... Sol. in acid. F=1.5 to 2. 2 3Fe2O3.2As2Os. p. Ext. Tab.{100>. 90°dist. yellow- G=3.27 F=3(?). Pleoc.: X=color- 3 2(Si,Zr)Oj on <100>= brown. less, Y= yellowish white, £j 65°, Z= wine-yellow. # 1.695 1.733 1.698 29°...... X=&...... Orth...... <110X011}tr... Emerald to H= 3.5 to 4 Sol.inHNOs. F=2to2.5. r 4CuO.As2O6.7H2O p>u rood. Z=c. Pris. c. leek green. G=3.39 Bright bluish green in sec- J» tion and faintly or non- pleoc. 1.730 1.699 49°...... {110>perf.at80° B 1 ac k ; in H=5to6.. Insol. in HC1. F=2.5 to a (Na.K)2O.(Fe,Mn)O. p Cn bO TABLE 7. Data for the determination of the nonopaque minerals Continued. to Biaxial positive group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a y ft Cleavage. Color. and specific Kemarks. composition. Dispersion. tion. habit. gravity.

B-0.025 1.70 90°±...... Y-6...... Mon...... {110}perf.at 60° H-5to6.. NasO.2FeO.Fe2O3. XAc=15°±. Fib. c. light green. G=3.2 in acid. F=3.5 with in­ 6SiO8 tumescence. Pleoc.: X= green to blue, Y= violet, o Z= violet, green to color­ less. B-0.05 1.70 85°± ...... X-6...... H-7...... 2GlO.FeO.2Y2O8. pv- {010}. Ext. Acic. c. perf. {100V yellow to G=3.18 hiortdahlite. Pleoc.: X= etc. <100>nearly fndist. colorless. colorless, Y= faint yellow, //. Ext.{010> Z= wine-yellow. = 4°. Disp. very strong. 1.701 1.706 1.703 Near 90°...... Trie.?...... H=6.5.... 10(Mg,Ca)O. pplagioclase. 1.700 1.706 1.702 Oto 60°...... X-c...... Orth...... H=6...... 4CaO.3Al2O3.6SiOz. pv X=6. Grains. tion. F=3.5 Pleoc. faint. strong. Y=c. Abnormal interference colors. 1.678 1.733 1.703 75°±...... X=6...... Orth...... <010>perf...... H=3...... 2(H,Na,K)!O. P>v. Z=o. Elong. < 001>imperf. G=3.4 3. Pleoc. : X= deep orange, 4(Fe,Mn,Mg)0. Blades c. y=lemon-yellow, Z= Ti02.4Si0 2 orange. 1.698 1.723 1.704 GO0...... Y-6...... {110} perf. at H=6...... CaO.2(Mg,Fe)O. p>v. ZAc=38° to Pris. c. 90°. G=3.4 acid. F=about 3. Tw. (Al,Fe)sO».3SiOi! 54°. Disp. pi. {100K001}. Colorless dist. in section. 1.700 1.724 1. 705 55°±...... X-6...... Mon...... H-5 3(Fe,Mn,Ca)O.P2O6 p>u rather T>isp. dist. darkens on G=3.G7 Colorless in section. strong. exposure. 1.708 1.745 1.708 Small...... Z=c...... Orth. Fib.c.. H-3to4. Fe2O8.P2Os.4H2O P>V strong.- Y=a. G=2.87 HOI but not in H2SO4. F=2.5 to 3. Pleoc.: X= very pale rose, Y= color­ less, Z=pale rose. Blue contains Mn. ^, t> 1.708 1.718 1.711 67°...... H=6 Gelat. Fus. Poly. tw. ^ 3MgO.CaO.2SiOj P>U weak. XAc=36°. Grains. G=3.15 verycbmmon. Tw.axisc, [-1 composition pl.{110> with tS angle 43° between sets. en Less common tw. pi. and composition pi. <100). g 1.709 1.724 1.711 23°...... do...... H-5 to 5.5 Sol. in HC1. F-2.5 to 3. ^ 2CaO.MnO.As2O5. P strong. ZAa=32°. Elong. 6. {100}imperf. brown. G=3.36 acid. F=3. Abnormal W interference colors. Fe^Os g = 3 per cent. I-H 1.74 1.72 Mic...... H-2.5 Decpd. by HC1. Infus. p> 2Fe2O3.2SiO2.3H2O P>U strong. after olivine. brown. G=2.8 Pleoc. in brown and H yellow. g 1.712 1.731 1.721 Adelite...... Very large. .... Y=6...... Mon.Tab.{001) None...... Gray...... H=5 Sol. inHNO8. F=easy. ^ ZAc=39°. 2MgO.2CaO.As3O5. pU rather brown. G=3.36 bluish green, Y=deep f> strong. .Disp. dist. brownish red, Z=deep t~i smoky gray to brownish en yellow. B=0.01 1.725± Trie...... {100>perf...... 3(Ca.Co,Mg)O.As2O5. P

1 Mineral name and 2V Optical orienta­ System and Hardness a 7 0 Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1 7*?^ 1.730 X=6...... <100}perf...... H-5 4(Mn,Fe)O.P2O5.H2O p>u extreme. ZAC=O±. reddish O=3.43 less in section. Disp. marked. brown.

1.713 1.746 62°...... Opt. pl.nearlv Trie. Pris. c. <001}perf...... H- 5.5 to <> (Mn,Fe,Ca)O.FesO». p>v strong. //{110> and {010}lessso. brownish G= 3.35 to acid. F= 3 to a black mag­ 4SiO2 <110>. black. 3.40 netic globule. Pleoc.: X= Ext.on{100>= strong emerald-green or 44° with c. dark blue-green, Y=palo Ext. on{010}= violet-brown or claret, Z- 31°. deep brown or pale brown.

1.734 1 729 81° to 90°..... Y=&...... {001>perf...... H=6.5 Epidote group. Insol. in 4CaO.3Al2Os.6SiO2. pu strong. ZA«=32°. red-brown. G=3.40 decpd. byHCl. F=about 6SiO».H20 3. Pleoc.: X= yellow, Y= violet, Z=red. 1.725 1. 7-10 1.73 Augite (titaniferous) . . 33°...... ZAc=42°...... Mon. Pris. c. -{U0>perf.at87° Black...... H=6 Pyroxene group. Contains CaO.2(Mg,Fe)O. G=3.39 4.8 1 per cent TiO2. Pleoc.: (Al.Fe),08. X= reddish or pinkish 3(Si,Ti)O8 brown with a violet shade, Y=reddish or pinkish brown with a violet shade, ,0 Z=pale bright yellow d with a brownish shade. 1.720 1 737 1.730 On<100>ZAc=32°±' Tric.Tab.<001> {HOWlTOVperf. H=6 MnO.SiOj {001>lessso. G=3.67 insol. in acid. F=2.5. Onj'OlO>ZAc= Data for fowlerite, a vari­ ety containing zinc. 1.73 Ottrelite...... YA&=O±..... <001>perf...... H=7 (Fe.Mn)O.Al2O8. p>v. ZAc=25°±. 0=3.3 toid. Decpd. by H2SO4. SSiOs.HjO Disp. strong. Nearly infus. Pleoc.: X= olive-green, Y=blue, Z= yellow-green. TABLES FOR DETERMINATION OF MINERALS. 229

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C-) tl 00 i-c 10 O ' to LI; o v. Y=6. { 100>, Ps. {100>imperf. red. G=3.64 Pleoc.: X= columbine-red, i i hex. from {OlO}poor. Y== orange-yellow,Z= O tw. emerald-green. 1.74 1.95 1.75± Small...... Y-a...... H=l Fe»O8.3MoO8. PU strong. ZAc=Oto21° Plates{001}. {443}imperf. G=3.55 H2SO4. Nearly infus. SiO2.H2O Disp. strong. Pleoc.: X= olive-green, Y=plum to indigo blue, Z= yellow to colorless. 1.743 1.78S 1.75± 39°...... X-c...... Orth. Pris. c. . -{120}dist...... H=6 Insol. in HC1. F=easy. Na2O.(Ti,Zr)O2. Z=h. G=3.42 Abs.: XZ. In sec­ 2SiO2 tion colorless. 1.744 1.760 1. 752 Daviesite ...... Near 90° ...... X=6...... Orth. Minute Colorless ...... Sol. in HNO8. Lead oxychloride. pU rather ZAC= 13°. G=3.80 moderate in Prussian blue strong. Disp. dist. Abs.: Xand Yimperf. .. Dark emerald- H=4.5 to Sol. in HC1. F=2. Pleoc.: 5CuO.P2O5.2H2O pperf..... Red to black.. H=6 Epidote group. Gelat. after 4CaO.3(Al,Mn,Fe)2O,. Y=6. tals,flb.'6. G=3.52 ignition. F=3. Pleoc. 6SiO2.H8O Disp. strong. strong: X= orange to cit­ ron yellow, Y= amethyst to pink, Z=red. TABLES FOR DETERMINATION OF MINERALS. 231

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me tio ) 48go -go »o s HO TO com ,^8* ^ s2-'? (1fe§ ^ H !lt-C^l fiSIM 1.87 1.93 1.88 35°...... X-6...... Orth. Pris. {OlOMist Brownish to H=3 Sol. in HC1 \vith evolution 6MnO.As»O6.5H2O p>v. Z=c. fib. garnet-red, of Cl. F=2(?). Red- alters black. brown in section and nonpleoc. 1.877 1.894 1.SS2 X-c...... Orth...... Derf<110> Yellow to H=6to7 Nearly insol. in acids. F= 8MnO.4Al2O3.8SiO2. P>v very X=c. dist. brown. G=3.62 2 to 2.5. Pleoc.: X=deep V,O5.5H20 strong . brownish yellow, Y= golden yellow, Z=pale yellow. Y-6...... Black. In H-5.5 Not attacked by acid. 2SiO2.SbjO6. P>V. Z A trace of Tab.<010>. splinters G=4.5 Pleoc. strong in red brown 2(AlFe),0». noo}=i4° blood red. to red yellow. Near man- 14(Mn,Fe,Ca)O to 15 °. Luster me­ ganostibiite and hema- Incl. disp. tallic. tostibiite. strong. 1.900 2.034 1.907± 77 J- Y _ 5 Mon...... {110} rather YelloWjbrown H=5 Sol.inH2SO4. F=3. Pleoc.: CaO.TiOj.SiOj p>u marked. ZAc=51. W e d g e - dist. colorless, etc G=3.5 X=nearly colorless, Y= shaped . pale greenish, etc., Z= flattened yellow, red, or pink. {001}, etc. 1.910 1.945 1.91 Tetrag...... {110H001}di. G= 3.85 to Volatile at 1. Tw.<100> 4.15 penet. 1.885 1.956 1.920 89°...... H=3.5 Faintly pleoc.in green. Abs.: 4PbO.2CuO.P2O5. pX. nHoO fcO CO Or to TABLE 7. Data for the determination of the nonopaque minerals Continued. 03 Biaxial positive group Continued.

Hardness Mineral name and 2V Optical orienta­ System and Remarks. T 0 Cleavage. Color. and specific composition. Dispersion. tion. habit. gravity.

B=0.04± 1.92± 3S°± ...... X=a...... Orth.C?).....-. {100>rather Deep red or H= 4 to 4.5 Sol. in acid. F=easy. (Mn,Fe)2O3.P-!O5. perf.,<{010> purple. G=3.4 Pleoc. intense: X= gray­ n2o less so. ish. Y and Z deep blood red.

1.93± 1.934. 10° ±...... Tetrag...... {110>rare...... Colorless, pink, H=7.5 Insol. in acid. Infus. Ab­ ZrO2.SiO2 Short prisms brown, etc. G=4.7 normally Max. (SeeUni- with pyra­ axial group, p. 190.) mids. 1.915 2 03 50°...... Y=b...... ^lll>dist...... Brownish black H=6.5 In sol. in acid. F=4to4.5. 15CaO.(Al,Fe,Y)2Og. p>u strong. G=3.52 to 15TiO2.16SiO 2 3.77 1.963 1 963 Small...... Two at 90° .... Colorless ...... H= 5 to 5.5 Insol. F=3(?). 9(Pb,Ba,Ca)O.B203 . P v very X=c. <110}dist. brown. G=3.65 2 to 2.5. Pleoc.: X=deep g V2O8.5H2O strong. brownish yellow, Y= gol­ £ den yellow,Z= pale yellow. t=3 w 2.00 Mon.(?) Six- One perf...... Olive-green, H=3 F=1.5(?). 6(Cu,Ca,Ba)O. P >v very plates. Disp. sided tablets. citron-yellow. G=3.55 £ V2O6.15H2O strong. very strong. CW TABLES FOR DETERMINATION OF MINERALS. 237

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' Mineral name and 2V Optical orienta­ System and Hardness a Kemarks. o 7 composition . Dispersion. tion. habit. Cleavage. Color. and specific w gravity. o Cfi o 2.24,; 2. 53Li 2.24 Li Small...... Y-6...... Orth ...... Black...... H-4 . Sol. in HC1. Infus. Red- o Mn2Os.H2O P >v (?)very Z=c. {IHHperi. G=4.3 brown and nearly opaque hd strong. in section. Abs. faint: X I I and Yporf...... H-4. 5 Nearly insol. in acid. Infus. MnO.(Ta,Cb)2O5 P v rather Z=r;. Short prisms. brown, G=5.9 to V265.H20 strong. black. 6.2 2.27 2.30 2.27 Raspite...... 0°±...... Y-6...... Mon...... {100>perf...... H- 2.5 Decpd. by HC1. F=2.5 to PbO.WOs XAC large. Tab.{lOO}. low. 3. Abs.: X and Y>Z. Elong. b. 2.24 2.31 2.27 90°±...... Z-c...... Orth. Fib. c.. {110} highly White...... Sol.inHNOs. F 1. 2PbO.PbCl, P. black. G=7.2 to ferberite. Sol. in conct. 7.5 H2SO4. F=3, Strongly pleoc. Abs.: X>Y>Z. B=\veak 2.33 90°±...... Z^b...... Orth...... H-5to6 Infus. Pleoc. weak: X= 7(Ca,Ce,Fe,Na2)O. X=a. Ps. isomet. {100)- less so. G=4.13 light gray-green, Z=dark 6Ti02.CbjO5 Cubes. gray-green. 2.30Li 2. 40i.i 2.35Li Nadorite...... Very large.. . . Y=b...... Orth...... \ 100}very perf . Smoky brown, H=4 Sol. in HC1. F=1.5. Tw. PbO-SboOs-PbCl. p>v strong. Z=c. Tab.{100>. brown-yel­ G=7.02 pi. {010} crosses at about Pris. c. low. 2.3Ui 2.46Li 2.36Li Mon...... H 5 to 5.5 Sol. in conct. H2SO*. F=3. (Fe,Mn)O.WO3 Tab.< 100>. black. G=7.2 to Nearly opaque. Abs.: 7.5. X>Y>Z. 2.2Su 2. 48Li 2.36Li ...... Mon. (?) Pris. Black...... F=1.5 (?). Pleoc. very 3(Pb,Mn,Fe)O. p>v rather strong: X=nearly color­ V265.H20(?) strong. less, Y= clouded reddish brown, Z=clear reddish brown. 2.31Li 2. 66Li 2.37Li 54°...... Y-n...... H 2.3 to 3 F=1.5. PbO.CrOj p>u very ZAC=-5V. distinct. G=6.0 strong. Disp. very strong. B=very 2.3S 90°±...... Z-a...... Orth. Ps. iso. H=5.5 Decpd. by H2SO4. Infus. weak. CaO.TiO2 Y=6. etc. G=4.03 May be . Complex in­ terlaced tw. 2.38Li 2.42Li 2.39Li 50°±...... Z-a...... H-6 Insol. in acid. Infus. 2Fe2O8.3TiOj X=e. . to black. 0=4.4 to Weakly pleoc. in reddish 5.0 brown" Abs.: XZ. 2.374 I 2.457 2.404 Stibiotantalite...... 75°...... X-a...... Orth...... { 100 } very perf. H=5 Isomor. with stibiocolum- Sb2O3.(Ta)Cb)2O5 P. 7.9 HF. F=4. Data for mineral with G=6.82, Ta2O5=39 per cent. 0 and disp. increase with Cb, B and G decrease. 2.398 i 2.459 2.419 73°...... Y-6...... Orth...... do...... H-5 Insol. in acid. F=4. Data Sb2O3.(Cb,Ta)3O5 p

2V ' Mineral name and Optical orienta­ System and Hardness ; a y ft Cleavage. Color. and specific Remarks, composition. Dispersion. tion. habit. gravity.

2.45j.i 2. Sin 2.45Li Orth. Pris. c. Black...... H=-5 Insol. in acid. Inl'ns. In 6FeO.Sb2O8.5TiO2 G=4.53 section dark brown and non-pleoc. 2.37 2.65 2.5 Yjcleav.(?).. Orth. Pris... {010}veryperf. Deep red, H=2to3 Sol. in acid. Volatile. HgO Z=elong. orange , brown.

2.583 2.741 ' 2.586 Brookite...... 30°Na...... Xr=&...... Orth...... {110}indist.... Brown, black. H=6...... Insol.. even in HF. Infus. TiO2 0 for yellow- Xbi=c. ° G=3.9 Plebc. weak. green. Disp. Z=o. very strong. 2. 51 Li 2.71M 2.61Li 90°±...... Y=a?...... Orth...... <100}perf. .... Yellow...... Soft Sol. in acid. F=1.5. Com­ PbO Disp. strong. Tab. {100}. G=9.29 monly bordered by lith­ arge. Pleoc.: Y=light sulphur-yellow, Z= deep yellow. Opt. for blue. B = ex­ >2.72Li 2E-700 ...... X-6...... {010} highly Lemon-yellow H-2 Sol. in H2SO<. F=l. Vol­ treme. As2Ss P>V strong. Z=a. Foliated. perf. G=3.4 atile. Luster on {010} pearly. 2.74 B = ex­ >2.72Li Small (?) ..... Elong.+ ...... Mon. Pris.... {100}perf...... Cherry-red. ... -11=1 to 1.5 F=l. Volatile. treme. Sb2O3.2Sb2S3. G = 4.5 B=very >2.72Li Med...... {010} tr...... Iron black, H= 2 to 2.5 Decpd. by HNO2. F=l. strong. Ag2S.Sb2S3 Streak cher­ G = 5.2 In section blood-red. ry-red. >2.72 B= ex­ >2.72U Z//elong...... Mon...... { 100} perf. .... Cochineal-red . H= 2 to 2.5 Sol. in HNO8 with separa­ treme. TloS.As2S8 G = 5..53 tion of S. F=l. Deep red in powder. Extreme Pyrostilpnite...... Ext. on...... Mon. or trie... {010} perf..... Hyacinth-red.. H=2...... F=l. Tw. pi. {100}. Ab­ 3Ag2S.Sb2S3 {010}= 8° G=4.2 sorption. toll" Biaxial negative group. [The minerals of this group are chiefly orthorhombic, monoclinic, or triclinic.]

1.394 1.396 Mirabilite...... 76°...... X-6orY=&.. -flOOVperf..... White...... 1 H=2 Sol. in H2O. F=1.5. Ef­ NasO.SOs.lOHsO ZAc=30°. Near p y- <001X010>tr. G= 1.481 floresces rapidly. Disp. strong. roxene. 1.407 1.415 1.414 £0°...... X/\c 52°... Mon ...... <001}perf. .... Colorless. H=2 Decpd . by H2S O4 . F= 1 .5. H NaF.CaF2.AlF3. H2O pv perc. {010} imperf. G=1.46 Rapidly loses HsO on exposure to air. Cfi 1 440 1 4C.O 40°...... Orth...... H= 2 to 2.5 Sol.inH.O. F=l. (Na,NH4,K)2O.SO3. o. G=1.4S lous, saline, and bitter. ^ // to 6. F=6.5. § B 1 410 1.458 1.457 White...... H=3 Soda alum. Sol. in H2O. » Na2O.Al2O3.4SO3. Disp. slight. Fib. G=1.88 F=l. > 22H2O t-1 'Ul 1 449 1.463 1.461 56°...... X-6...... Mon...... do...... H=3 Artificial. Sol. in H2O. Na2O.Al2O3.4SO3. Disp. slight. YAC=SO°. Laths {100}, G=1.73 F=l. Alters in air to 22H2O elong. c. tamarugite. 1.462 1.471 Soft. 2Al2Os.SO8.15HsO Fib. to 242 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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Borax...... Creedite...... (Ca.K^Na^O.AljOs- Gmelinite...... 2A1(F,OH).S03. Goslarite...... Ptilolite...... Daraoskite...... Kalicinite...... Mineralandname O.2BONa.10H32 ,Ca)O.Al(NaO23. 0 MgO.Al.4SOO32. .4SOMnO.AlO2a3. composition. W 4SiOO.6H2 CaO.2CaF2. 10SiOO.5H2 022±H2 22±H02 0 £ O2H2 co c 1- ' 6- 'aE HCS^ A fl .!> Z^ .2 N « CO p PH <

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^ OO ^J1 ^ ^i ^J» *-* OO P . O) t Jj 8 iH OO iH iH rH iH CO * (J 1 _P TH J 1 TABLES FOR DETERMINATION OF MINERALS. 243

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s s TABLE 7. Data for the determination of the nonopaque minerals Continued. to

Biaxial negative group Continued.

Hardness Mineral name and 2V Optical orienta­ System and a 7 0 Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

B=0.015 1.501 81°...... Y=6 <010>{110}fair . Dark gray..... H=5 Iiisol. in acid. F= dif . Tw. 2CaO.3Al2Os.9SiO2 p>u. XAc=40°. G=2.71 pi. {110} universal, {OIO} less common. C: 1.412 1.526 1.501 53°...... X-o...... Orth. Elong.c. imperf. G=1.84 Infus. 1.490 1.511 1.502± Z-6...... Green...... H=4to5 Serpentine. Decpd.by HC1. 3MgO.3SiOs.2H2O X=c. G=2.6± F=dif. Faintly pleoc. 1.334 1. 506 1.505 Niter...... 7"...... Orth. Equant Colorless ...... H=2 Sol. in H2O. Tastes saline. K2O.N2O5 Pu small. XAC= 8°. Tab.{001>. <110>dist. G=2.13 Disp.dist. 1.420 1.524 1.506 48°...... Orth...... <010>dif...... White...... H=1.5 Sol. inH2O. F=1.5. Na2O.CO2.H2O P or G=1.55 O 1.344 1.506 1.506 Colorless ...... Sol. in H2O. Tastes bitter. ^ MgO.N505.«H2O p^ B =0.011 1.506 50°...... Orth. Fib ... White ...... Soft. asepiolite. Separates gelat. ,0 2MgO.3SiO2.4H2O SiO2 in acid. 1.495 1.514 1.508 Manganese chalcan- Trie H=2 to 3 Sol. in H2O. F=3. Near thite. p>u. G=2.10 chalcanthite. MnO.SO3.5H2O 1.502 1.512 1.510 44°...... H=4 Zeolite. Decpd. bv acid. CaO.Al203.6SiO2. p strong. G=2.25 F=3. 5H2O 1.495 1.520 1.51 70°...... Y=6...... Mon. Rhombic {001>good...... do...... H=2 Easily sol . in acid. B . b. de­ 2CaO.3B2O3.13H30 p. G=1.87 crepitates and fuses with c. much intumescence. Al­ ters to meyerhofferite. 1.49 1.521 1.510 69° X-c...... Orth ...... {001}peri...... G=2.50 Pleoc.: X=pale yellow, Y Ca0.2U03.P206. Ps-tetrag. <100}good. green. and Z=deep yellow. Be­ comes uniaxial in a desic­ cator.

1.512 1.515 1.514 Orth. Fib. c. White, etc.... H=5 Zeolite group. Gelat. F= CaO.2SiO2.2H2O G= 2.17 to 2.5. 2.36 1.470 1.516 0"±...... _ -, Mon. (?)...... H=1.5 Infus. On standing in oils Al2O3.3±SiO2. Plates{001}. yellow, G=2.6 jS increases to 1.60. (See 3±H2O brown. p. 193.) 1.444 1.523 34°...... X-b...... Colorless. H=2to3 Slightly sol. in H2O. Soi Na2O.CaO.2CO2. p

1.519 1.529 I CO Z-c...... do...... H- 2 to 2.5 /3 scpiolitc. Does not gclat. _ 2MgO.3SiOj.2H2O G=2 with acid. £j 1.616 1.520 1.52 36°...... ,... Trie...... G = 2.57 Feldspar group. Artificial. ^ Na2O.Al2O3.2SiO2 tion. Tw. as rnicrocline. Also £j ZAtw.=44°. at 60°. v^ 1.513 1.5X5 1.524 Y-t...... {010XUO}very White, etc .... H=4 Zeolite. Gelat. F=2. Tw. § CaO.Al2Oa.4SiO2. P G=2.3 4H3O 30°. nnperf. $ GO 1.518 1.526 1.524 YorZ-6..... Mon...... < 010X001 >perf. H-6 Feldspar group. Insol. in K2O.AhO3.6SiO2 Disp. weak. less, pink, G=2.56 acids. F=5. Tw.ax. cand etc. composition pi. {010 >, others less common. 1.522 1 530 S30...... {010X001 >perf. H=6 Feldspar group. Insol. in K2O.Al2O3.6SiO2 p>u weak. 15°. etc. G=2.56 acids. Infus. Tw. pi. Ext. on{010H {010}, also {100}, both bO 5° to 6°. polv., giving a very fine ^ grating. Cn TABLE 7. Data for the determination of the nonopaqtie minerals Continued. 05 Biaxial negative group Continued.

Hardness ig i Mineral name and 2V Optical orienta­ System and a 0 Cleavage. Color. and specific Remarks. O 7 composition. Dispersion. tion. habit. gravity. O tn O 1 ^0*1 1 <151 1 ^OQ 32" to 54°...... Ext.on{001}- Trie...... {010X001 }perf. White, etc .... H=6 Feldspar group. Insol. in O (Na,K)2O.Al203. p>v weak. l°tot>°. G=2.5S acids. Infus. Tw. pi. I I 6SiO2 Ext. on{010>= {010}, also {100}, both 6° to 10°. poly., giving a very line Q grating. O 1.51S 1.542 1.530 X-b...... Alon. or trie... {010}nerf...... Blue...... Very sol. in cold H2O. V2O4.3SOs.16HzO ZAfib. 12°. Fib. F=easv. Pleoc. strong: Rhombs. X=deep blue, Y=pale blue, Z=nearly colorless. B- 0.003 1.532 Milarite...... Small...... 7«=*c...... Ps. hex...... Pale grnen . H=6 Insol. in acid. F=3. Basal (H,K)2O.2CaO. etc. G=2.57 section shows six biax. Al2O8.12SiO2 segments. Uniax. at high temp. 1 pcrf...... H-3 Slightlv sol. in H2O. Sol. in NaijO.CaO.2SOa p>u strong. YAc=14.2. Tab. {001}. G=2.83 HC1.' F= 1.5 to 2. Disp. strong. i *;i^ 1.535 1 CQO Large(?)...... White...... H=soft Na2O.B2O3.4SiO2. sol . in H2O . F= easy . 2H2O 1.489 1.557 1.534 Y usually // Orth. Fib...... do...... H=2 2MgO.CO2.4H2O fibers. G=2.03 1 541 1.534 Mod...... Trie H 2 to 3 thite. G=2.1 less in section. Near chal- ZnO.CuO.2SOg. canthite. 10H2O

i *yifl I ccn 1 t&t\ 79°...... Trie...... <010}perf...... H-2 2CaO.3B2O3.7H2O p>v perc. Z'Ac=2V. Pris. c. G=2.12 easy with intumescence to Ext.on{OUH. Tab.<100}.. an opaque enamel. Al­ X'Ac=33°. teration of inyoite. 1.423 1.555 1.536 42°...... X-o...... Orth...... {110} very H=1.5 Sol.inH2O. F=5.5. (NH4)SO.2CO2.H2O pv weak. white. G=2.2 chalcanthite. 1.534 1.540 1.538 Cordierite...... 78°±...... X=c...... Orth...... {010>dist...... Blue, green- H=7 Partly decpd. by acids. 4(Mg,Fe)O.4Al2O3. p

B= 0.008 1.539 QQO X=6...... Mon. Tetrag. None...... Colorless...... H= 4.5 to 5 Gelat. F=3. Section {001} CaO.Al2O3.4SiO2. pu. Y^c=5 to G=2.80 clase. Difficultly fus. In­ 4SiO2(?) 24°. sol. in acids. Tw. axis c and composition pi. {010}: to also other laws. TABLE 7. Data for the determination of the nonopaque minerals Continued. to ^ OO Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a V ft Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1 539 Z-b...... H-2 Sol. in dilute acid. F=3 2CaO.P2O5.5H2O YAa=15J°. tened<010}. <301}perf. pearly. G=2.21 with intumescence. 1.520 1.572 1.547 Copiapite...... : 90°±...... X=c...... Orth ...... <001 V...... Sulphur-y e 1 - H=2.5 Janosite. Sol. in acid. 2Fe2O3.5SO3. pO med. Z bisects Tab. {001} low. G=2.10 F=4.5to5. Pleoc. in thick 18±H2O acute angle. Scales,crusts plates: Yellow to colorless. 1.439 1.595 1.547 60°...... X-c...... <001>imperf. .. White ...... H=soft Sol. in H2O. F=easy. (NH4)2O.C2O3.H2O p. G= 1.46 to 1.50 1.531 1.552 1.549 Cobalt chalcanthite.. . Mod...... Trie...... Rose-pink..... H=2to3 Near chalcanthite. Sol. in CoO.SOs.5HaO Not strong. G=2.2 H2O. F=3. 1.538 1.554 1.549 53°...... X-c...... Orth. Ps. tet- <110}perf...... White...... H=4 Gclat. F=5. BaO.Al2O3.3SiO». ppearly. b or tab­ |lOO>good, lets-} 001 >. {110>poor. H-5 Not attacked by HC1. Eas­ (Ca,Na2)O.2Si02 Z_L laths. Fib. Laths c. blue to dark G=2.55 ily fus. to a glass. Color­ blue. less in section. 1.54 1.560 Jeflerisite 0±...... Mic...... {010>mic...... White, green, H=1.5 Vermiculite. Alteration of 5(Mg,Fe)O. brown, etc. G~2.30 mica. Decpd. by HC1. 2(Al,Fe)-iO3.5SiO!. Heated at 300" C., exfoli­ , HHjO ates very remarkably. On higher heating fuses. B=mod. 1.56 ...... Soft Between kaolinite and non- (Al,Fe)2O3.2Si02. Hex. plates. G=2.+ tronite. Decpd. by HC1. 2H2O Scales. F=dif. 1.552 1.563 1.562 40°± ...... X=c...... {010}dist...... Blue, etc...... H=7 Partly decpd. by acids' 4(Mg,Fe)O.4Al203. p

1.548 1.567 1.562 70°±...... Trie In two direc­ Flesh-red, yel­ H=3 Partly sol. in H2O. F=1.5. 2CaO.MgO.K2O. Fib. 6. tions. low, etc. G=2.78 4S03.2H2O Tab.{010}. 1.561 1.567 1.565 6S°...... Z-b...... Mon ...... {001>perf...... White...... H=2 Insol. in acids. Infus. Al2O3.2SiO2.2H2O p>v weak. X A c=4°. Minute hex. G=2.6 YAa=ll°. plates {001 >. 1.569 1.569 X-6...... {001X010>porf. H=5.5 Partly sol. in acids. F=2.5 Na2O.2GlO.6SiOs p G=3.55 to 3. Tw.{001}at 60. H2O Elong. a. 1.485 1.572 1.565 Small...... {OCl>mic...... Soft Chlorite group. Gelat. F= 4(Mg,Fe,Ca)O. PIates, G=2.31 4. Pleoc.: X=pale yel­ (Al,Fe)2O3.5SiO2. shreds. lowish, Y= olive green, 7HsO Z= brownish green. B= 1.57± 0 to 40°...... X=a...... Orth.?...... {100}perf...... G=2.3 Serpentine. Easily sol. in 0.025± Silicate of Fe,Mg,Al, Z=c. Tab.{001>. HC1. F=dif. Pleoc.: X H. and Y= green or yellow, Z= green or dark red-yel­ low. 1.560 1.571 1.570 X=6...... {010>...... Serpentine. Decpd. by HC1 3MgO.2SiO2.2H2O Z=c. Fib. c. G=2.6± or H2SO<. Faintly pleoc. 1.524 1.583 1.571 52°...... Trie {010}perf...... H=3to3.5 Sol. in H2O. F=4.5 to 5. FeO.Fe2O3.4SO3. P>U very bisects obtuse Tab.{001}. brown. G=2.15± Very pronounced abnor­ 14HaO strong. angle be­ mal interference colors in tween {100V some sections. {010}. X or Z AC=33°. Disp. mkd.

fcO TABLE 7. Data for the determination of the nonopaque minerals Continued. to CM Biaxial negative group Continued. o

Mineral name and 2V Optical orienta­ System and Hardness a 7 0 Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.555 1.575 1.572 42°...... X= sensibly Trie...... { 001}{ 110} Yellowish..... H=soft 3MgO.(NH4)2O. Disp. slight. n o r m a 1 to Slender {110>{130}. G=1.89 2P2O6.10H2O perf. cleav. prisms. YAelong.=33°. Plates. 1.566 1.576 1.572 82°...... On {Old}X'A Trie...... {100}perf...... Colorless, etc . . H=6 Feldspar group. AbaiAnao. AbAn4 {001}= 33°. {010}good. G=2.73 Gelat. F=5. Tw.{010}. On {001 }X' A poly., almost universal. {010H22 0. Other tw. laws common. l.Sfi 1.580 1.574 62°...... X-6...... {010}{1PO}{001} Yellow...... G-=3.10 Pleoc.: X=pale yeUow, Y CaO.2UO3.P2Oe. and Z=deep yellow. 8H2O H=4 Insol. in acid. F=easy. 3Al2O3.2Na2O.4P2OB . G=2.9 6CaF2.17H2O 1.541 1.574 1.574 Oto50°...... XAc=3°±.... Mon. Tab.... {001 }very perf. Black, etc. .... H=3 Mica group. Decpd. by K2O.4(Mg,Fe)O. pu perc. Z=a. tablets {001}. phur yellow. G=3.1 on {001} pearly. Nearly tct- rag. I 1.562 1.588 1.576 Sphaerite...... Large ...... Z=c...... Orth. Concre­ One dist ...... Gray to blue.. H=4 5A1SO8.2P2O6.16H2O tions. Fib. c. G=2.54 1.576 1.579 1.578 0±...... XAC=O°±.... Mon. Shreds. H=2.o Chlorite group. Decpd. by 5(Mg,Fe)O.Al2O8. P>V perc. <7=2.7 H2SO4. F=dif. Abnormal 3Si02.4H20 blue interference colors without ext.. Pleoc.: X= nearly colorless, Y and Z= green. TABLES FOR DETERMINATION OF MINERALS. 251

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Jeiekite...... Leverrierite...... Uranospinite...... ^hopeite...... Peganite...... Anorthite...... Lucinite...... (Cr.Fe.Al)O.2SiOt.82 A10(F,OH)24. Nontronite...... (Ca,Mg)O.2Fe3O8. CuO.Na2O.2SO». .20SiO4AlO28. CaO^UOa-As^e. .6H2A1O.P285 3"(L'i,fC)O.2FeO.2 3HO.8(Li,K)F2 AlO.3±SiO28. 3ZnO.P.4HO25 CaO.Al.2SiOOs82 A1.4HO.P285 2Na2O.CaO. i 8SiO.7±HOa2 c 2±HO2 1 (/ 2HO2 1 PjOs 8HO2 O2H2 I i'o

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3 X o 8 S § S i 1 1 1 S rl I ^ r4 ^ - -; ^ -; i ^ C2 P: TABLE 7. Data for the determination of the nonopaque minerals Continued.

Biaxial negative group Continued.

Hardness Mineral name and 2V Optical orienta­ System and a T P Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1 19 1.613 1.5S7 X-c...... Orth. Thin {001}mic...... White...... II- 3 La2O8.3CO2.9H2O pO weak. 7=6. plates{001>. G=2.60 to 2.74 1.552 1.600 1. 5SS X=c...... Orth. Tab. {001}dninent.. White, gray, H= I to 2 Difficultly sol. in H2SOL Al2O8.4SiO2.n2O p>v wealc. Z // length. {001}. apple-green, G=2.8to F= difficult. Blades and etc. Pearly. 2.9 fib. I con 1.589 1.589 Talc...... X=c...... Mon.f?)...... {001}mic...... H-l 3MgO.4SiO2.H2O p~>v pcrc. Orth.(?) G=2.7. luster.

1 CQO 1 %QA 1.589 77°...... Z-J)...... White...... H-2 2CaO.As2O5.5H2O p>V. XAc=70°. G=2.7 ter on -{010} pearly. 1 C79 1.59 1.591 36°±...... X-6...... {100>pcrf...... Grayish...... H-3 3ZnO.P2O6..}H2O pu perc. XAC=O±. lets{001>. G=2.9± F=5.7. Tw. pl.<001}. 2H3O

1 £fl 1.600 Soft (Ca.Mg)O.2Fe2O3. Z//elong. and fibers. green to yel­ G=2.50 to yellow orange, Y= 8SiO2.7±H2O low or orange. orauge-yellow, Z= yellow­ ish green to bright green. Data from partly altered mineral. 1.54 1 **Q Med...... ^ _ c H-2 12(Mg,Fe)O.2Al2O3. Z // fibers. {001}. Fib. G=2.8± 9SiO2.9H20 1 C7O 1.594 090 H-3 5CaO.6B 2Os.9H2O p». tetrah. red. G=3.4 to F=2.5. 8HSO 3.6 1.579 1.597 1.593 Ax.pl. 12J° to White...... H=6 Sol. in H«SO4. F=2. Poly, AljO3.P2Oi.2LiF p>u small. <100>, 67° to {100}less so. G=3.05 tw. in two directions at {001}. X to {02l}rare. 90°. edge {100} <001}isll.84. Disp. strong. 1.55 1.594 1.594 0 to 57°...... X-c...... Plates and {001}mic...... Copper-red, H=3 Mica group. Insol. in acid. 6(H.K)20.2MgO. P>U weak. scales. purple, etc. G=2.84 F=3. Pleoc. slight. 3AlsO8.12SiOj 1.570 1.597 1.594 30°...... Orth...... Lauie'lar...... Greenish yel­ H=3.o Insol. in acid. F=3.5. (Na,K)2O.FeO. P>upcrc. Radiating low. G=2.78 Pleoc.: X=nearly color­ (Al.Fe)»02.5Pi(),. globules, less, Y and Z= siskin- H»O plates, and green. fibers. 1.594 40°...... X-c...... {001}mic...... Green...... H=2.5 Mica group. Near musco- Chromium mica. p>u strong. G=2.86 vite. Insol.in acid. F=5. Pleoc.: X = robin 's-egg blue, Y= yellowish green, Z= bluish chrome-green. 1.575 1.611 1.594 S7°...... X-b...... Yellow...... H=2 to 2 Sol. in HC1. Infus. Pleoc.: RO.U03.SO3.4H20 p>u strong. YAc=7°. Laths{010}. G=3.9± X= colorless, Y=pale yel­ R=Cu,Fe,Na2 Disp. strong Elong. c. low, Z= canary - yellow. Poly. tw. {100}. 1.571 1.598 1.595 39°...... X-c...... Orth...... <00l}perf...... Green to pale H=4 Insol. in acids. F=3. Tw. GlO.CaO.2SiO2.NaF p>u weak. Z=6. Tab.{COl}. {021}<201> yellow. G=2.96 pi. {110} or {001}frequent. {100} {010} dist. 1.592 1.599 1.597 70"± ...... X c H=7 Partly dccpd. by HC1. 4(Mg,Fe)O.4Al2O3. pu. Hex. plates let. G=2.9 in HC1. F=2.5. Pleoc.: 2(K,Li)F <001}. X= colorless, Y and Z= pink. to CO 254 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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fQ pq TABLES FOR DETERMINATION OF MINERALS. 255 ?:*?§W itsi* . 1it i. Eilli!^ii *'!;! Ii11 i2 ipt^: «§>| . terd "A 3 2fc -3 aM&o .">> ^2 ^x. 1 S a ffil'a2S(u !!> E i !'O Iffl II ! S..fl3« 49«03'Ol| t d k- »g£X,2 IP^ to! 8 lift A t ill irtM "-I £ nil . jig !fl3j.SK |fc&3 | SS --5 1.2 SB ISlSS -3!! 11 1.SKSB §§1 3 Qw> coSw CQ < i- pa 2 0S i-H 41 o CO 8 1C CD O O on *s>o o 10 JC« V c*i?a locicoco ^co ^wJ cv ci c*m to eo cv gy>) ^ CO n i 1! tN II tl II II II II II II I II II II II II 1 II II II o Bo Wo Wd W6 wo wo Wo W6 wo Wd

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n n TABLE 7. Data for the determination of the nonopaque minerals Continued. to Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a T 0 Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

B=0.037± 1.625 X-c...... {001}perf..... H- 2 to 2.5 Pleoc.: X= green, Y and 3(Ni, Mg)O.2SiO2. Plates {001 >.. Also one // brown. G= 2.47 to Z= yellow green. 2H2O opt. pi. 3.24 Q 1.625 X-6...... {00l>perf...... H-4.5 strong. 2FeO.3MnO.3CaO. p>u very YAc=-15°. Tab. {010 >. {010}fair. G=2.92 green, Y= yellow-brown, 2A12O3.4P2O5. strong. Crossed disp. slightly greenish, Z= 10H2O chestnut-brown . 1.611 1.636 1.627 78°...... Y-6...... {110} at 124° H-6 CaO.3(Mg,Fe)O. Pu perc. XAc=32°. Tab. {100} {001} less so. G=2.9 pure artificial mineral. or {001}. Decpd. by HC1. F=4. Elong. 6. Tw. pi. <100}. 1.60 1.63 1.63± Mariposite...... o±...... X=c...... {001}mic...... H=5 Mica group. Near alurgite. Chromiferous mica. Hex. plates green. G=2.79 Insol. in acid. F=3. {001 >. Pleoc.: Z>YandX. 1.5»> 1.630 1.630 Troegerite...... 0±...... X=c...... Mon.?...... {001}perf. .... Soft...... Sol. inHCl. F-2.5. 3UO3.As2Oi.l2H2O Ps. tetrag. {100} good. G=3.23 Tab.{001>. 1.602 1.632 1.632 Bementite ...... 0±...... X i flat face of Orth...... H=6 8MnO.7SiOj.5HaO fib. Fib., plates. G= 2.83 to to a black glass. Faintly Z or Y= 3.11. pleoc. Abs.: Xand Y1.64 1.63 Bityite...... X=c...... H-5.5 7(H2,Li2,Ca.Gl)O. Z A {1010}= G=3.05 section divided into six 4Al203.5Sio2 sectors, and these show poly. tw. with tw. pi. {10TO}. TABLES FOB DETEEMINATION OF MINEBALS. 257

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12097° 21 17 258 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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< andname fc C SO osition. 5d Al, _E :Sw c3 03 n) 9H s_> H M e-, 0) *-> SS ine co |4 IS* Ss= 25 s^ «<03 oc» 1.624 ' 1.647 1.647 X-c...... Orth ...... {001} mic ..... G ray to brown I H= 6 Deepd. by acid. F= easy. 8MnO.7SiO».5H2O Plates{001}, {010} {100} Weathers I G=3.11 fib. perf. darker. ; 1.643 1.649 1.649 Small...... Mon...... {00!} mic. .... Dark green. ... H 3...... Chlorite group. Decpd. bv 3FeO.Al2O3.2Si02. Fib. and hot HCl. Pleoc.: X=pale 3H2O plates. yellowish, Y and Z= olive- green. 1.585 1.660 1.649 Mon...... <001}oerf...... Emerald-green H=2.5 Sol. in HCl. F=3.5 Pleoc.: 3CuO.2SO3.6H2O PY Sba >Z. Tsv.pl. {001}. inH B=0. 03 1.65 Friedelite...... Small...... Trig...... {0001} pert..... Rose-red...... H=4to5 Decpd. by HCl. F=4 (to a 9MnO.8SiO3.MnCl2. G=3.07 black glass). Anom.biax. 7H2O Pleoc.: X= colorless, Y O andZ=greenish yellow. W

1.625 1.655 1.65 33°...... X nearly i {001}dist..... Greenish yel­ H=2.5 to Decpd. by HCl. Infus. S {001}. Fib., etc. low, earthy. 4.5 Pleoc.: X= nearly color­ ts G=1.7 to less, Y and Z= yellow to 2.4 greenish yellow. w 1.610 1.6S2 1. 650 {001} very peri. White, yellow, H=ltol.5 g 5Na3O.20b2O5. pJ 5As8O5.55H2O green. 2.98 pleoc. 1 1 1.625 1.669 1.653 74°...... Y=-6...... Mon...... Colorless...... H=5 Gelat. F= 2 to 2.5. H 2CaO.2SiOij.BzOs. P>U weak. ZAc=-l°to Elong. c. G=3.0 4°. W Disp. perc. cn 1.62 1.6S9 1.654 Cabrerite...... 90°±...... Mon...... {010}perf...... Apple-green. . . H=2 Near annabergite. Sol. in 3(Ni,Mg)O.As2O6. p>v strong. Fib. c. H= 2.96 to HCl. F=4to5. 8H2O D i s p~~. 3.11 marked. 1.647 1.660 1.654 74°...... X-h...... Mon...... {100}ratherperf Orange, red, H=5 Sol. in acid. F=3. Pleoc. 5MnO.2P8O6.5H2O p

Mineral name and Hardness a y /3 2V Optical orienta­ System and Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.633 1.662 1.655 Eosphorite...... 51°±...... X=b...... Orth ...... {100>nearlyperf Rose, pink, H=5 Sol. in HC1. F=4. Pleoc. 2MnO.Al2O3.PjOB. p Hex. tablets brown, cop­ 0 = 3.0 Intus. Pleoc. feeble: X= 4SiO2.3H2O small. <001>. per-red. colorless, Y and Z=pale brownish-yellow. 1.622 1.687 1.658 Annabergite...... 84°...... X=6...... <010}perf...... H= 2.5 to 3 Sol. iuHCl. F=4. 3NiO.As2O6.8HsO p>v rather ZAedge36°± Plates^ 010}, O=3.0 to o strong. Disp. elong. c. 3.1. V marked. o *i 1.648 1.660 1.660 18° to 35"...... Y-b...... <001}perf...... H-5 12(Mg,Ca)O. P. Hex.tablcts. dark green.' 0=3.0 bertite. Lnsol. in acid. fel 6(Al.Fe)zOa. small. Infus. Pleoc.: X=pale 5SiO2.4H2O orange-yellow, Y and 7i o pale green. 1.340 1. 675 1.660 Tilasite...... 83°...... Pale srrecn H-5 Sol. in acids. .F=4to5(?). 2CaO.MgO.As2O6. 0 = 3.77 MgF2 1.649 1.661 1.660 20° to 40° ..... Y-6...... 14(Mg,Ca)O.8Al2O2. p0.5°. Tab. {001>. G=3.09 acid. Infus. Pleoc. :X= 5SiO2.4H2O reddish-brown, Y and Z= green. Tw after mica law, polysynthetic. 1.C3 1.69 1.60 Stewartite ...... Very large .... X nearly j_ Trie ...... {OlOVgood..... Yellow ...... O-2.94 Pleoc.: X*=colorless. Y= 3MnO.P2O5.4H2O(?) Disp. strong. <100>. Tab. {100}. very pale yellow, Z=vel- On cleav. Fib. low. XAc=56°. Cleav. shows an opt.axis in field. 1.626 1.699 1.GG1 90° 4- 1 ^ _ jj Mon...... <010* highly Crimson to 11=2 Sol. in HOI. K=2. Pleoc. p>u weak. Pris. c. Verti­ perf. gray. G=2.95 strong: X--*pale pink, Y= cally stri­ very pale violet. Z=red. ated. Abs.: X and Yu. Z=a. 0 = 3.2 1.520 1.667 1.667 X-c...... do...... H=4 Sol. in nci. F=dif. Z=a. SrO.COs P 6JI.O 3.96 canary-yellow, Z= canary- H X near a. yellow. Abnormal blue interference color. ,_, 1.635 1. 702 1.6GS 87°...... X-??...... {010}perf...... Pale indigo, H=2.5 Decpd. by HC1. In/us. 6 3FeO.As3O6.8H8O p>u rather ZAc=32°. Pris. c. green. G=2.96 Pleoc.: X=deep blue, Y= VJ strong. colorless, Z= yellowish to oil-green. g 1.658 1.670 1.669 Z-c...... White...... 0=3.7 Alters on exposure to air. g ZnO.SOs p Na.O.4(Mg,Fe)O. PO.CO| p>u weak. Elong. c. 0 = 3.71 eral with CaO=17.6,BaO= W 4.S.54, SrO=4.2.i, CO»= 29.41. 1.634 1.685 1.673 Durangite...... 45°...... Y=6...... Mon...... Orange-red. . . . H=5 Decpd. by H3SO4. F=2. NasO.2AlFO.AsaO5 p

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a illl -< ^ ^ PQ P 1.678 ' 1.6SS 1.685 Axinite...... 71°± Trie...... {001 V{ 130} Colorless, H=7 Insol. in acid. F=2. 6(Ca,Fe,Mn)O. pV very ZAelong. va­ Laths {010}. Z=canary yellow. Very carbonate. strong. ries greatly abnormal interference Crossed very with color colors and no extinction strong. of light. in white light on face. <010>. Poly. tw. (100K?)- 1.610 1.70» 1.685 Y-ft...... Green...... H=3 Mica group. Insol. in acid. 2K8O.2AlsO3. p>v strong. XAc=Otol°. Plates{001>. 0 = 2.97 F=3(?). Pleoc.: X=olive- (Mg,Fe)O.3VaO8. green, Z=green brown. 10SiO2.4±H2O Apple-green interference color is characteristic. 1.67 1.698 1.686 Trichalcite...... Xi plates. .... Orth. Plates. Verdegris H=2.5 Easily sol. in HOI. F=2 3CuO.As2O6.5H»O Y // length. green. to 2.5. In section pale bluish green and non- pleoc. 1.678 1.689 | 1.686 30° to 40°...... XAC-O°±.... Blue, green­ H=7 Insol. in acid. Infus. Pleoc.: 8A12O3. B2O3.6SiOs. pPharmacosiderite ..... Large...... Ext. large. .... {100}imperf. .. Olive-green, i H=2.5 Sol. in HC1. F=1.5 to 2. p>v very Y=&(?). Ps. isomet. brown, yel- G= 2.9 to Divided into cubic seg­ strong. Disp. strong. Cubic. low. 3.0 ments and these show to poly. tw. Abnormal in­ C: terference colors. Co TABLE 7. Data for the determination of the nonopaque minerals Continued. to Oi Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness at T 0 Cleavage. Color. and specific Remarks. O composition. Dispersion. tion. habit. gravity.

1.676 1.708 1-694 Kaersutite ...... 82°...... On{llO}ZAc= Mon. Pris. c. {110} perf. at Black...... H=6 Amphibole group. Fus. Titaniferous horn­ Disp. weak. 8°. 124°. G=3.14 readily to a black mag­ blende. netic "bead. Pleoc.: X= 1 light brown, Y=darlc red­ Q dish brown, Z= darker reddish brown. B=low 1.695 Riebeckite...... Large...... X=6...... Mon. Fib; c...... do...... Black, blue. . . H=4 Amphibole group. Insol. Na2O.FeO.Fe2O8. ZAc=4°. G=3.2to in acid. F=3(?). Pleoc.: 5SiO2 3.3 X=deep blue to smoky green, Y= yellowish to brownish yellow, Z=vefy dark smoky green to black. O 1.677 1.708 1.695 Basaltic hornblende. . . Large ...... Y=6...... Mon. Pris. c...... do...... Brownish H=tt Amphibole group. Insol . in tej Silicate of Fe,Al,Mg, pArfvedsonite ...... Large ...... Y=6"...... Mon. Pris. c...... do...... do...... H=6 Amphibole group . Insol . in Silicate of Fe,Na,Al, XAc=-12° G=3.45 acid. F=2. Pleoc.: X= Ca, Mg. to 15°. greenish blue, Y=laven- o'er blue, Z= green yellow. B=mod. 1.702 Triphylite...... C to 34°...... X=c...... Orth...... {001 }perf ...... Greenish gray, H=5 1 Isomor. with lithiophilite, Li2O.2FeO.P20& p>v very Z=b, {010} nearly bluish. G=3.55 ' which is opt.+ and has a strong. perf.{110}iu- lower n. Sol. in acid. terrupted. . F= 1.5. 1.692 1.705 72°...... X=o...... Orth. Pris. c. 1 {H0>perf.at90° Greenish...... ] H=5.5 Pyroxene group. Isompr. (Mg,Fe)O.SiO2 p>v. Z=c. G=3.o with enstatite. Nearly in- I sol. in acid. F=5. Data for mineral with FeO= 22.6 per cent. As iron increases B increases, 2V decreases-pleoc. increases. Pleoc.: X=clear red, Y= yellow, Z=green. 1.713 50°...... Ext. on {010} Trie...... {001 >perf ...... Colorless, vel- H=4 Sol. in dil. HC1. F=easy. 4ZnO.PjOi.HsO One bar in- 25°with{100} 1 o w i s h , G=4.15 dicat es and 10° with brownish. P>V weak. {001 >. The other Ext. {100 > 26° CO P and 14° with tj {010>. o Disp. strong. 'a» 1.687 1.708 1.707 Bar ke vikite KAO X-6...... {110> perf. at H=6 Amphibole group. Pleoc.: Between hornblende ZAc=12° to 124°. G=3.43 X= bright brownish yel­ and arfvedsonite. 14°. low, Y= reddish brown, Z=deep brown. 1.705 1.711 1.709 69°...... Y=6...... Mon. Tab. None...... Pale blue, H=7.5 Insol. in acids. Infus. 5MgO.6Al2O3.2SiO2 p. green. G=3.45 Plooc.: X= light greenish Disp. perc. blue. Y=blue, Z=blue or X= light greenish blue, Y=dark pure green, Z= yellow, faded green. 1.660 1.760 1.710 X=6...... Mon. Laths {010>perf.(?).. Apricot, yellow H=3 Pleoc.: X= colorless, Y= UOs.SOa.CHjO Slight. ZAc=40°. {010>.Elong. c. pale orange-yellow, Z= deep orange-yellow.

1.703 1.722 1 711 X=c...... Orth. Stri­ {001}highly Emerald-green H=2 i Sol. in dil. acids. F=2. 4CuO.N2O6.3H2O p G=3.43 Pleoc.: X and Y= green, strong. zontally. less so. Z=blue. 1.697 Orth...... Blue...... H-3 to 4 , Sol. in HC1. F=2.5 to 3. erous). Disp. strong. Pleoc.: X=very pale vio­ ' (Fe,Mn)2O3.P2Os. G=2.8 let, Y= violet, Z= deep 4HSO blue. 1.700 1.726 71° to 79°...... Z-b...... Mon. Tab. {010}dist..... Light yellow, H=6 1 Pyroxene group. Sol. in lOCaO.NasO.lOSiOj. p.3NaF weak: X and Y=light i wine-yellow,Z=deep wine- 1 yellow. fcO Oi TABLE 7. Data for the determination of the nonopaque minerals Continued. fcO O5 Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness « 7 0 Cleavage. Color. and specific Remarks. o composition. Dispersion. tion. habit. gravity.

1 T9Q 1 719 81° to 90°..... Y-6...... H-7 4CaO.3Al2O3.6SiO2. p>u strong. ZAc=2°. G=3.36 HC1. F=3to4. H2G 1.715 1.720 1 719 H-6.5 Partly decpd. by HC1. F=3. 12CaO.3Al2O3. G=3.4 Anom. biax. Piece, slight. 10SiO2.H2O 1.715 1 79^ 83°...... {0001}dist..... H-6 Sol.jnHCl. F dif. Basal (Mn,Ca)O.G10. X nearly i Thick tablets G=3.47 section shows three radial SiO2 <0001>. {0001}. segments. 1.712 1 79ft 1.720 82°...... Trie Blsdos H-4 to 7 "Al2O3.SiO2 p>u slight. <1CC}. {100}. {010} less so. G=3.6 faint: X= colorless, Y= Ext. on {100 } Elong. c. {001 }parting. violet blue,Z=cobalt-blue. ZAc= 30°±. (1) Tw. pi. composition Disp. dist. face {100}; (2) tw. axes {100} {001}; composition f ace{ 100 }; (3) tw. and com­ position pi. { 001 }poly . , etc. 1.691 1.720 1.720 0±...... X=6...... Mon.(?) Plates Sol.inHCl. F-3(?). Pleoc. 3U03.P8O5.6H2O p > u very Disp. strong. {010}. yellow. strong: X=nearly colorless, strong. Y and Z= canary-yellow. 1.686 1.735 1.722 Glaucochroite ...... 61°...... X=6...... Orth. Pris. c.. Bluish green . . H=6 Easily sol. in HC1. F=3. CaO.MnO.SiOs p>u marked Z=a. G=3.41 1.680 1.752 1.725 Basaltic hornblende. . . 79°±...... Y=&...... Mon. Pris. c. . {110} perf. at Brownish H=6 Amphibole group. Insol. in Silicate of Fe,Al,Mg, pu strong. Z=a. {001},elong.6. sky blue. G=3.02to F=2 to 2.5. Pleoc.: X= Fan-shaped 3.10 grass-gi'een, Y= yellowish aggregates. green, Z= grass-green. 1.711 1.740 1.727 Picrotephroite ...... 85°...... X-6...... {010} dist ..... Red, brown... H=6 Olivine group. Gelat. F= 2(Mn,Mg)O.SiO2 p>u. Z=a. G=4.0 3 to 4. Data for mineral with percentages of Mg2SiO<=40.4; Mn2SiO4= 59.6. i.7a5 1.730 1.729 24° <001}mic Brown ...... H=4 Gelat. F=3. Pleoc.: X= 6H2O.7MnO.AlsOa. pV. ZAc=ll° to Fib. 124°. G=3.5 black, magnetic glass. 15°. Pleoc. : X and Y= colorless , Z= yellow to brown . Tw. pl.{ 100}polysynthetic. 1.760 1.730 80°...... On {110}...... {110} perf. at Black...... H=6 Amphibole group. Titamferous liorn- Weak. Pris. c. 124°. 0 = 3.34 ] = readily to a black blende. magnetic bead. Pleoc.: X=pale olive-brown or olive-green, Y= brown, Z=dark brown, almost opaque. 1.710 1.732 1.731 Y=6...... Blue...... H= 2.5 to 3 F=1.5. In section pale CuO.SeOs.2H2O P>U ext. G=3.76 greenish blue and non- pleoc. 1.723 ..» 1.734 Med...... Z-c...... Orth.(?).. .. Colorless ...... Sol. in HC1. Infus. 8(Mn,Mg,Zn)O. PU strong. X=o. Elong. b. tinuous. colorless, etc. G=4.35 1.715 1.75 ..78. {001} perf..... Pink to pale. H=5 Gelat. Fus. readilv to a 3(Zn,Mn)O.SiO2. p>u rather cleav. plate. Pyram. reddish G=3.9l brown enamel. H30 strong. brown. 1.715 L«, !.» Sickl elite Orth.(?)...... Two unequal Dark brown, H=4 Sol. in acid. Fus. easilv. 6MnO.Fe2O3.4P2O6. p >u very at 90°. etc. G=3.45 Pleoc.: Yellow to orange- 3(Li,H)2O strong. red. Abs.: X>Y>Z. 1.640 ,,«, L» 40°...... X-6...... {100} perf..... White, grav, H= 2 to 2.5 Sol.inHCl. Inins. 5ZnO.2CO2.3H2O oO rather {110}imperf. G=3.5 to F=3. Pleoc.: X=pale 3(M,Ce.Fe,T>i)2O3. strong. 4.2 yellowish or pale greenish, 6SiO2.HsO Y and Z= brownish red or green. fcO O5 TABLE 7. -Datafor the determination of the nonopaqiie 'minerals Continued. to C5 Biaxial negative group Continued. 00

Mineral name and 2V Optical orienta­ System and Hardness a V ft Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.733 1.744 1.740 Rhodonite ...... On {100}Z'Ac {110}{110}perf. Red, etc...... R=6 Pyroxene group. Nearly MnO.SiOs p

B= rather 1.71 Vilateite...... P>U strong . . . Ext. sma.ll.... Mon ...... Violet, etc. . . . Manganese streugifce. Com­ strong. Mn2O8.P2O5.4H2O G=2.75 pare with blue strengite. Pleoc. slight; rose tint // c. 1.74± X-ft...... Orth...... {010}{001}fair. Yellow...... G= 2.74 0=1.713(0), 1.715(B), 1.770 K2O.CrO3 p>u weak. Z=c. (F). 1.655 1.744 1.740 Aurichalcite ...'...... Very small.... Pale green or H=2 Sol. in acid. Infus. Pleoc.: 5(Zn,Cu)O.2CO2. P blue. G= 3.54 to X= nearly colorless, Y 3H2O Fib. c. 3.64 and Z=pale greenish. O 1.71 1.70 1.74 Iddingsite...... Large ...... X j_ plates.... Pscudomorph Mic...... Reddish H=2.5 Decpd. by HC1. Infus. 2Fe2O3.2SiO2.3HsO pv strong. Y=c. Elong. c. G=3.7 Pleoc.: X=pale green to o yellow, Y= bright green to greenish yellow,Z= yellow d to yellowish green. hj B=0.03 1.750 80°...... Y-b...... {100} good..... Yellow to H=6 Pyroxene group. Diffi­ (Mn2,Zr,Ca2,Na<)O2. Disp. weak. XAc=-20°. Tab. {100}. brown, col­ G=3.5 cultly sol. in IIC1. Fus. (Si,Zr)O, orless. Tw. pi. {100} lamellar. B Pleoc.: X= colorless to clear wine-yellow, Y= col­ t8 i orless to greenish yellow, * Z= gold en or brownish- B yellow to orange-red. W 1.729 1.768 1.754 Y-,6...... Pistachio- H=6 Epidote group. Partly 4CaO.3(Al,i-e)2O3. P>U rather XAC=-2.5°. Elong. ,">. {100}impcrf. green. G=3.4 decpd. by HC1. F=3 to 6?iO..H2O strong. 4. Pleoc!: X=colorless, Y=pale greenish yellow, Z= colorless, etc. 1.74S 1.761 1.751 Nearly 60* .... Orth...... None...... | Colorless...... H=4.5 Somewhat sol. in hot dilute XajO.SOa. P>V rather * HC1. F=1.5 to 2. Com­ Pb(On)Cl strong. plex tw. or similar struc­ ture. 1.70S 1.798 1.760 81°...... X=c...... Orth ...... {OOlVvery perf. Blue to green­ H= 2.5 to 3 Sol.inHCl. F=3.5. Pleoc. 4CuO.SOs.4H3O Z=o. Laths {010V <010>. ish blue. G = 3.49 faint in pale blue. Abr-.: elong. a. Fib. Xu strong. Z near 6. Crystals, green. G = 4.0 to Pleoc, faint. X = bluish crusts, fibers. 4.4 freen, Y=yellowish green, W =deep bluish green. F 1.760 1.768 1.76S Oto32°...... Trig...... {0001> perf. Red, blue, etc. H=9 Insol. in acid. Infas. Pleoc. CO A1203 Anom. biax. parting. G=4.0 faint. 1.745 1.782 1.770 {110> perf. at B r ow n i s h H=6 PjToxene group. Compare O ous). P>U strong. Pris. c. 89*. black. G=3.55 with acmite. Insol. in Na^O.(Fe.V)208. acid. F=3.5. Pleoc.: 4Si0 2 X=dark brown, Y= light SomeCaO.MgO. brown, Z=pale yellowish H 2SiOs brown. W 1.751 1.782 1.771 74°...... Mon ...... One imperf. . . . Light purplish H=6 Gelat. F=3. Pleoc. slight 7(Mn,Zn.Ca)O. P>V slight. Massive. red. G = 3.85 in pale rose to colorless. i i 3Si02.HsO 1.729 1.807 1.773 83°...... Trie...... H= 2.5 to 3 F=dif. in oxidizing flame. PbO.2(Ca,Mn)O. pAllactite...... 4°Na - ...... {lOlVdist...... Brownish-red. H=4.5 Easily sol. F=2(?). Pleoc. 7MnO.As2O6.4H2O 0 for green. yellow Z=6 Pris. c. { 100 > less so. G=3.84 weak in hyacinth-red and p > u very and XAc = olive-green. Nearly color­ strong. 49.2°. For less in section. blue Y=6.« 1.757 1.803 1.78 Thortveitite...... 80°...... X=c...... Orth...... { 110} good..... Grayish green. H=6to7 Near thalenite. Slowly sol. (Sc,Y)2O3.2SiO s Z=a. Pris. Radial G=3.57 in acid. F=easv. Tw. rosettes. 1 pi. < 110), fcO OS o Krenner, J., Beitrag zur Kenntniss der optLschen Verhaltnisse des Allaktites: Zeitschr. Kryst. Min., vol. 10, pp. 83--84, 1885. Dona and' others quote Krenner incorrectly. CD 270 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

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8 .ggg g S | g | PQ 1.788 1.830 1.81 Hancockite 50°...... Y-b...... Mon...... JQ01 V Brownish-red . H=6 to 7 Epidote group. Gelat. in 4(Pb. Ca,Sr)O. p>u perc. G=4.03 acid after ignition. F= 3. 3(Al,Fe, Mn)2O3. Pleoc. in reddish brown. 6SiO2.H2O Abs.: Z>X. 1.775 1.825 1.815 50°...... Yin (010)..... Mon .... {010>poor(?).. Red-orange to H=2>, Readily sol. in HsO. Pleoc.: 3V2O6.2CaO.llH2O p>u very Disp. ext. y e 1 1 o w - G=2.46 X= light cadmium- yel­ strong. orange. low, Y= cadmium- yel­ low, Z= orange. H 1.715 1.820 1.817 Orth...... {0001}dist-... Ocher-yellow, H=3 Alunite group. Sol. in HC1. K5O.3FejO3.4SO3. Opt. pi. //edge. Hex. tablets brown. G=3.2 F=4.5. Basal section C 6HSO and fibers. divided into six segments. f Faintly pleoc.: X= nearly H colorless, Y and Z=pafe CO yellowish.

1.800 1.840 1.831 X-o...... Orth...... Malachite to H=4.5 Sol. in acid. F=3. Pleoc.: 6 2CuO.2CaO.As2O5. p>u rather Y=6. Stout prisms. yellow-green. G=4.33 X=green, Y=yellow- w H2O strong. green, Z= blue-green. o 1.750 1.832 1.832 Vcrv small X-c...... Orth...... {0001} perf..... Yellow, brown H=3 Alunite group. Sol. in HC1. H NasO.3Fe2O3.4SO3. Hex. tablets. G=3.2 F--=3. Faintly pleoc.: X tei 6H2O ' = nearly colorless, Y and Z=pale yellowish. g 1.805 1.847 1.838 X-o...... Orth...... Gray, etc H=6.5 Olivine group. Gelat. F= 2(Fe,Mn,Mg)0. pO mod. Z=6. Equant. G=3.9 to 3. Data for mineral with > SiO2 4.17 percentages of Mg»SiO4= H 7.5 per cent, Mn2SiO4= H-1 26.7; Fe2SiO4=65.8. O

1.809 1.859 1.838 80°...... Z=b...... Mon...... {100} very perf. Deep sky-blue. H=2.5 Partly sol. in HNO3. F= 5PbO.2CuO.3SO3. pu very Disp. strong. Sheaf-like G=3.1) Pleoc. in thick sections: 8H2O strong. aggregates. X = colorless, Z = pale green. Section { 010 } gives no extinction in white light but very abnormal red, blue, and green inter­ to ference colors. -j TABLE 7. Data for the determination of the nonopaque minerals Continued. fcO 7 Biaxial negative group Continued. to

Mineral name and 2V Optical orienta­ System and Hardness a 7 ft Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.825 1.857 1.842 86°...... Y-ft...... {lOOVimperf... Dark golden H=3 to 4 Sol. in hot H2O, with separa­ 15CaO.7I2O6.8CrO3 pU very Z near o. perf. green. G=4.19to blue-gieen, Y=light blue- strong. Disp. 4.38 green, Z= benzol -green. small. 1.670 1.895 1.870± 36°...... X-c...... Orth. Plates Soft. Pleoc.: X=nearly colorless, 'Ca0.2U03.V2Os. P>I> rather Y bisects {001}. Elon­ Y = canary - yellow, Z = 8±H2O strong. acute angle gated or darker canary-yellow. of rhombs rhombic. or //length. 1.786 1.875 1.S75 Small...... Ps. trig. Hex. {1011}...... 0=3.63 Alunite group. Sol. in HC1. PbO.3Fe2O8.4SO8. plates. Pleoc.: X=pale golden 6H2O vellow. Y and Z=dark brownish red. Basal plates divided in hexag­ onal segments. 1.655 1.909 1.875 Malachite...... 43°...... Y=6...... Mon. Pris. c. {001}perf...... H-4 Sol. with effervescence. F= 2CuO.C02.H2O pv large. Pleoc.: X= {001}. nearly colorless, Y=yel- "lowish green, Z=deep green. TABLES FOR DETERMINATION OF MINERALS. 273

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is? PQ 12007° 21- 18 TABLE 7. Data for the determination of the nonopaque minerals Continued. to Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a 7 0 Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

1.702 1.965 1.955 Durdenite...... 22°...... Orth...... IT- 2 to 2.5 FesOa.3TeO2.4H2O p>u very low. X= nearly colorless, Y= strong. pale yellowish with a greenish tinge, Z= rather pale sulphur-yellow. 1.96 Med...... X-c...... H-4 2PbO.3Fe2O3. Disp. abnor­ rhombs,etc. black. G=4.1 in hot dilute HC1. F=. As2O6.2SO3.6H2O mal. 3.5. Base divided into six biax. segments. Abnor­ mal interference, colors. Complex twinning. .1.947 1.968 1.961 Alamosite...... 65°...... Y=i!>...... {010}perf...... H-4.5 PbO.SiOj pV perc. Tab. {100>, G=6.l to HC1. F=2. elong. 6. 6.8 1.90 2.05± 2.00± Trie...... {010}dist...... H-3.5 Tw. pl.{010}. F-1.5. 5BioO3.3UO8.2As2O5. {010}. Tab. {010}. 0=5.8 12H2O elong. c. 1.87 2.01 2.00 Leadhillite...... 10°...... XAc-5'.o..... {001} very ir-2.5 4PbO.SO8.2CO2.H2O p

I QfU 2.078 2. 070 8°...... X-c...... Orth. Pris. c. {1 10X021 }dist. Colorless...... H=3 Sol. in dil. HNO3. F=1.5. PbO.COj P>u large. Z=a. G=6.5

1 QC 2.10 2.09± 20°±...... Y-6...... {010}perf...... H=5. In section colorless. Hydrated ferric tel- p>u strong. X nearly j_ plates. Other less so. green. lurite. to a cleav. B-0.01 2.09± Tend to lie Fib...... Yellowish- Soft Sol. in dilute HC1. F=1.5. BisO3.TeO3.2H2O p

1.70 O OO 1 v>° Orth. (?)...... Red...... G=2.51 Slightly sol. in B2O. Fus. CaO.3V2O6.9H2O Z I/ elong. Broad blades. easily. Pleoc.: X= light orange-yellow, Y and Z= deep red.

1.816 2 126 ('% Z=6...... {001 }dist ...... Colorless...... H=3 Sol. in HNO3. PbO.2PbCl2.H2O XAO.{1W}=6°. Tab.{100}. G=5.88

2.077 2.158 2.116 OOO X-a...... {100}dist...... do...... H=3 Sol. in HNO3. F= 1. Tw. PbCl2.PbO.H20 Z=c. Pris. b or G=6.05 pi. {001}. tab.{100}. 2 1 IS 2 10 = 2.13 X=c...... Ps. hex...... {10ll}imperf. . Yellow to H=3.5 Isomor. with pyromorphite, 9PbO.3As2O*.PbCl2 Pyr. c. brown. G=7.1 vanadinite, etc. Sol. in HNO3. F=l. Basal sect. in six segments with ax. pi. // edges of hexagon. 2.04 2.15 0±...... _ ,, {001}perf...... H=3 Decpd. by HNO 3 . Fus. PbO.PbCb G=7.21 easily. 13=0.05± 2.16± Massive ...... Colorless, etc. . H=4 Sol. in HNO3. F=1.5. Bi2O3.CO2.nH2O(?) Fibers. G=7.0± May be in part amor­ phous.

2.16 Ps. hex...... {0001}good. ... Yellow to H=3.5 Sol. in HC1. Volatile. Hg,NH4, and Cl. p

-afcO Cn TABLE 7. Data for the determination of the nonopaque minerals Continued. Biaxial negative group Continued.

Mineral name and 2V Optical orienta­ System and Hardness a T ' composition. Cleavage. Color. and specific Remarks. Dispersion. tion. habit. gravity.

1.77 2.35 2.18 Hewettite...... Orth...... CaO.3V2O6.9H2O Slender readily to a red liquid. blades. Pleoc.: X and Y=very light orange-yellow, Z= dark red. 2.00Li 2 35Li 2.18u Tellurite...... 90°...... Orth...... Wliite H-2 Fus Flexible TeO2 P>V mod. Z=c. Tab.{OiO>, G=5.90 acic. c. 2.13 2.20 2.19 Baddelevite...... ZrO2 " 30°...... XAc-120 ....- H a e p>u rather Y=b. Tab.{100>. black. G=5.7± Nearly infus. Poly. tw. strong. {100}and{110}. 1.94 2.51 2.20 Lemdocrocite ...... 83°...... X-b...... Orth...... H-4 Fe2O3.H2O Disp. slight. Y=a. Blades {010} {OOl^perf. dull orange. G=4.1 low, Y= red-orange, Z= elong. c. <100>good. orange-red. Abs.: X

2.11 2.22 2.22 NearO...... H o 5(Pb,Cn)O.2CrO3. small. brown black. G=6.0± Pleoc.: X=pale greeii, Z=pale brown. Abs.: Z>X. Tw. pi. {102>. 2.15 2.23 2.22 Goethite (impure) ..... Small...... Orth. Tetrag. {010>perf ...... H-5 Fe2O3.H2O+«H2O Disp. strong. same. G=3.8± X= clear yellow, Y= brownish yellow, Z= orange yellow. 2.09 2.26 2.24 Tungstite...... Med. small.... Orth...... H-2.5 WO3.H2O pY>Z. 2.17 2.32 2.26 H-3'to4 Sol. in dilute HNO.,. F- 2PbO.2CuO.V2O*. p>v very Stalactites, green, brown. G=6.1 1.5. Pleoc. marked: X= H2O strong. fib. very pale yellow. Y and Z=deep reddish brown. 2.2« Fib...... __ A f rt A C BijO3.CO2.7»H2O(?) G=6.9± be in part amorphous. TABLES FOR DETERMINATION OF MINERALS. 277

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00 t^ J? ,s iJ? CO U?1 00 '"t* 9fl-f ,^- SS IN CN CNCN (N rt - O II 53 -T TT Ti g tN CN CN CN IN CN' CN W j| ~" ^5 i3 CN CN ^ -g TABLE 7. Data for the determination of the nonopaQUe minerals Continued. ~ato Biaxial negative group Continued. oo

Mineral name and 2V Optical orienta­ System and Hardness a T (S Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

o xft, . 2.60i,i Smitbite (?)...... 26"±...... Y ft jj _ 2 Ag2S.As2S3 P>V strong. ZAc=6°. Hex. tablets. milion,streak G = 4.88 Trechmarinite (p. 144). same. 2.46Li 2 6lL,i 2.59Li 40°u±...... Y-b...... n-1.5to2 Sol. in alkalies. F=l. Vol­ AsS P>U very .XAe=ll°. Short prisms c. perf. Sectile. orange - yel- O = 3.56 atile. Pleoc.: X=nearly strong. Hisp. strong. low. colorless, Y and Z=pale golden yellow. 2.35^ 2.66L j 900. ; <101>perf...... n-2to3 Hg2OCl Pdis(;...... H--2to3 Sol. in HN O8. F-l. In sec­ treme. 3Ag»S.AsjSs Pgood..... Scarlet to H= 1.5 to 2 Pleoc. very weak. Abs. 2.779Li 3. 073u 3.063Li (Tl,Ag,Cu)2S.PbS. p

1.427 H-4.5 Insol. in HC1. Infus. Opt. (Na»,Mg)F,. G=2.61 anom. Divides into sec­ 3A1(/,OH)3.2H2O tions corresponding to oct. Alteration of cryo­ lite...... do...... MnO.SOa.7HjO Fib. exposure. 1.472 1.474 1.473 Flokite...... Z-b...... {100>{010}perf...... do...... H-5 (Ca,Na2)O.AljO8. XAc=o°. 0=2.10 with intumescence. Tw. 9SiO2.6H2O pi. Cross sections di­ vided into segments with different optical orienta­ tion. Opt.-f at 117° C. B-0.02 1.48 TTlriTlfT _L White, vellow- H-2to3 4AI2OS.3P2O5.30H2O ishjgrcenish. G=1.96 35 --fepble 1.500 Ext. 35° to 39°. Tib...... H-2 FeO.Fe2O3.4SO3. low. G=1.S75 24H2O 1.51 H=3 Hvdrous silicate of line. ish-black. G=2.5to part amorphous. FeOJ Fe2O8,MgO. 3.0 1 ^94- Ext. II...... Fib...... White...... H=2 5MgO.Al2Os.6SiO2. Elong.+ 0=2.19 4HSO Ilesite...... Mon. (?)...... (Mn, Zn, Fe)O.SO3. Pris. on exposure. 4HSO B=0.01 1.537 Fib...... H-6 Si02 G=2.6 B-0.02± H-5.3 Sol. in HC1. Infus. A12O3.P2O5.6H2O line fi b., greenish, G=?.H7 to plates. yellowish. ~4 CD 280 MICROSCOPIC DETERMINATION OF NONOPAQUE MINERALS.

£ > t. p'-i °. 1 1 |F|.I J t/ M. 1 cr 5 « andyellownonp Compare.with( f 1transparentlite aoidFiis.1hvf. i Sftp.tordinnm. instructuresec! "e t P* SiOofIno2. itedbementiteto base,f:on acid.FstrongL Remarks. h- c E '1 « E t ^ gs| w OS ;p.196). S t ' | > > fT 1 1 q | .£ f 9 "c & = V *- 1 & * S S § 1 g^^2 "!" C c' *o « 23P5 t H- V C ? P P. P c m la *t o o c *^ IT *«i£ u- S » -H* (O V n. -91^ >2 ^ e- TP C Si! m ft T 7 i 7 i oio: f o4 N Ci- m U5 W|M EC 0* & o c {r 0 tE c" EI 0 {= c tto tc tS C S ^ & 0 ^ - § | 1 t 1 s i _o . P fr & c PS ? e I o PE? ^§ §3 i &!0 ej S I I ^A S o ' 2 *V EH a i K- ~ § c t? | £ . S S 10. » || ? f e-s "3 1 1 S c 75 ~- ^M o 1i 'ft JC ^^ P ^ 03 1 1 6 1 c. ? 1° I II | S

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O c S Bakerite...... 8Ca0.5B0.6Si023. Crestmonte...... Riversidite...... 12MnO.SSiOa.7H.jO Podolite...... --.---..- Koninckite...... Mineralandname ^ 0.3A1K0.4S032. 4CaO.4SiO.7HO2 10CaO.3PiO.CO52 composition. lyOfiwipif.o...- Os.6H2OFeO.P23 A1O.2H23 ^ §^ A 9H02 O6H2 s s§ 2 'c 9 §6 1 (N C H C £

-H *i {- c >o i tc CO : ! 5 rH

- 1 S ^sct? ! ? -H c*: ira g S Cd , d i u? CC o ' «? 0 II « Orth ...... SoI.inHjO. Unstable. KCl.NH4Cl.FeCk. Oct. H2O fl-mod. 1.70±(?) Mon...... Emerald to H= 2 to 2.5 Sol. inHCl. Infus. Hydrous sulphate apple green. G=3.19 of U and Cu. 1.725 Ext. on best... Fib...... X fib. distinct, Flesh-red, lav­ H=4 Sol. in acid. 6RO.2P2O5.RF2. Cleav. 45° // fib. less so. ender. G=3.64 R=Fe>Mn>Ca.

B-0.01 1.73-b Fib...... White, earthy. H= 4 to 5.5 Insol. in HC1. Infus. Sb2O4.7iH2O G=5.1to 5.3 1.72 1.80 1.75± Yellow, earthy Soft Sol. in acid. UO3.CO2. G=4.82 1.76 1.81 l.S±" Brown, vellow, Soft 2Fe2O3.SO3.6H2O(?) black," dull green. l.S3tol.S7 H=6 Insol. in HC1. Fus. Opt. 5CaO.3Sb2O» Oct. G=5.0 anorn. Divides in to sec­ tions which show poly, tw. lamellae parallel to the edges. 0 decreases as H Na2O increases. 1.88 Cryptocrystal- Dark green to H=4 F=2.5. § strong. 2CuO.Fe2O3.As2O*. greenish yel­ G=3.9 2H2O low. B-0.01± 1.91 .....do...... Gray powder.. H=2 Sol. inHCl. F=1.5(?). 2Bi2O3.BiCl3.3H2O(?) G=6.4 0 ...... Hex...... Red, yellow, Unstable. FeCk brown. G=2.80 Unstable. 2CuO.SO3 Orth ...... Pale blue- Effloresces in contact with CuO.SOs green. air. 2.0± Bindheimite( ?)...... Gray...... H=4 F=3to4. Antimonate of Pb-f- G= 4.5 to 5 i H20 to 00 TABLE 7. Data for the determination of the nonopaque minerals Continued. fcO 00 Minerals of unknown optical character Continued. to

Mineral name and 2V Optical orienta­ System and Hardness a 7 P Cleavage. Color. and specific Remarks. composition. Dispersion. tion. habit. gravity.

B= strong 2.05 Fib...... Partly sol. in H2O. Sol. CaO.V2O4.5V2O5. in acid to a green solution. 14HSO B= weak 2.09 Brown, yellow H-6.5 Insol. Infus. 2CaO.Sb2O4 Oct. G= 1.1 2.08 2.16 2.1 Y-6...... {010} very perf. Sulphur-yellow H=2to3 Sol. in acid. 6PbO.2MnO. Ext. 45°. Domatic. (10l}lessso. to brownish. G=8.28 3As2O5.H2O B= strong 2 15 Cryptocrystal- 11-4.5 CuO.\VO3.2H20 line. Fib. (?) (?) Rhagite...... Cryptocrys- Yellow, green . TT=5 5Bi2O3.2As2O3. talline aggre­ G=6.82 9H2O(?) gates. B=mod. 2.25± Cryptocrvf- ...... Gray,etc. Dull H=4to4.5 Sol. in acid. F=-1.5. Bi2O3.CO2.H 2O(?) tallinc. G = 6.Sto 77 (?) (?) (?) Ochrolite ...... Orth...... Sulphur-y e 1- 4PbO.Sb2O3.2PbCl2 Thick tab. low. {001 >. B= strong 2.40U Ferberite...... Black...... H=4 Translucent only in thin­ FeO.WOa G = 6.64 nest edges with reddish colors. Pleoc. B=weak. 2. 42u X/ /fibers..... Cryptocrvstal- Vivid red, H= 2 to 3 F= 1.5. Abnormal green in­ Pb304 line. 'Fib., strealc orange- G=4.6 terference color. Pleoc.: yellow. Nearly colorless to deep reddish brown. B= strong 2.45± Li Columbite...... Orth...... {100>good..... 11=6 Insol. in acid. Infus. G in­ (Fe.Mn)O. (! = 5.48± dicates about 10 per cent (Cb,Ta)2O» Ta-sOs. Nearly opaque and dark red on thin edges. B=\ve.ik. H=2to2 Decpd. by acid. Volatile. Hg^CljO low. Dark­ G=8.33 ens on ex­ posure. H=3to3.5 Sol. in HC1. F=easy. 3PbO.2CrO3 hyacinth red. G=5.75 B= mod. . 2.G2±i Mon.C?)...... H=5 to 6 Decpd. by hot H2SO4. FejO3.3TiO2 G=-1.25 Translucent only in very thin edges in blood red. Pleoc. weak. Abs.: X

B= strong 2.63red {pin. laths ext. .Laths. <001>lessso. Abs. very strong:Xporf...... H=3 Sol.inHNO3. F=i. Nearly strong. 2PbO.As2O3 gray, streak G=5.5.5 to opaque in section and reddish 5.57 slightly pleoc. brown. B=very Extr. 'frig...... H=oto6 Infus. Nearly opaque. strong. FeO.TiOs G=4.7±

O Extr. Orth...... ...... H= O Sol.inHNO3. F=l. PbS.As2S3 Needles. G=5.4 Extr. Orth...... <001>p3rf...... Pinchbeck- Opaque to translucent in Ag2Fe5S, Tab. \ 001 >. brown to greenish gray. black. Extr. Vrhail-p Orth...... H=3.5 Sol. in HC1. Fus. easy. TIASzSbSft gray to red­ G=5.30 dish.

10 00 Co

INDEX.

A. Page. Acmite=aegirite...... 35,270 Antlerite...... 40,229 Actinolite...... 256 Apatite...... 197 Adamite...... 35,229,267 Apatite group...... 196-199 (passim) Adelite...... 35,227 Aphrosiderite...... 41,216 Adularia= orthoclase...... 245 Aphthitalite...... 186 Aegirite (aegirine)...... 35,270 Apjohnite...... 41,242 Aegirite-augite...... 225 Apophyllite...... 186,193 Aegirite (vanadiferous)...... 269 Aragonite...... 262 Aenigmatite=enigmatite...... 71,233 Arcanite...... 207 Aeschynite= eschynite...... 72,183 Ardennite...... 232,233,235,236 Agnolitc, near inesite. Arfvedsonite...... 264 Agricolite...... 35,236 Arizom'te...... 41,283 Akermanite...... 188 Armangite...... 201 Alabandite...... 35,184 Arseniopleite...... 41,190,232 Alam osite...... 274 Arseniosiderite...... 42,201,202,273 Albite...... 210 Arsenolite...... 77 Alexandrite= chrysoberyl...... 230 Artinite...... 45,246 Allactite...... 35,269 Ascharite...... 42,248 Allanite...... 35,176,177,229,267 Astrolite...... 42,253 Allophane...... 172,173 Astrophyllite...... 226 Almandite...... 178,179 Atacamite...... 272 Alum...... 171 Atelestite...... 42,237 Ahimian...... 38,187 Atopite= romeite (?)...... 128,179,281 Aluminite...... 205 Auerlite...... 42,189 Alunite...... 187 Augelite...... '...... 213 Alunite group...... 187-202 (passim), < Augite...... 226,228 218,223,271-274 (passim) Aurichalcite...... 43,268 Alunogen...... 206 Automolite=gahnite...... 178 Alurgite...... 39,253 Autunite...... 250 Amarantite...... 39,254 Axial angle, relation between, and indices of Amber= succinite...... 174 refraction...... 10-12 Amblygonite...... 253 measurement of...... 24 American Museum of Natural History, Axinite...... 263 acknowledgments...... 8,34 Azurite...... 43,230 Amesite...... 188,195,215 B. Ampangabdite...... 39,181 Amphibole group...... 214-233,255-267 (passim) Babingtonite...... 43,228 Analcite (analcine)...... 72,192,243 Baddeieyite...... 43,276 Anapaite...... 39,216. Bakerite...... 43,280 Anatasc...... 204 Barite...... 219 Ancylite...... 39,190,234 Barkevikite...... 265 Andalusite...... 258 Barrandite...... 44,220 Andesine...... 212 Barthite...... 44,231,232 Andradite...... 40,179 Barylite...... 224 Anemonsitc...... 212 Barysilite...... 44,202 Anglesite...... 235 Barytocalcite...... 262 Anhydrite...... 213 Basaltic hornblende...... 264,266 Ankcritc...... 40,199,200 Bassetite...... 250 Annabergite...... 40,260,262 Bastite, variety of serpentine. Aiineroidite, mixture of columbitc and samar- Bastnaesite-...... 44,189 skite. Bauxite...... 280 Anorthite...... 251 Bavenite...... 44,213 Anorthoclasc...... 246 Bayldouite...... I...... 45,236 Anthophylh'te...... 2.19 Bazzite...... 196 Antigorite...... 244,249 Beaverite...... 45,201 285 286 INDEX.

Page. Page. Bechilite (doubtful)...... :... 45 Calomel...... 191 Beckelite...... 179 Cancrinite...... 193 Bellite...... 45,203 Canfleld, F. A.,acknowledgments...... 8,34 Belonesite=sellaite...... 185 Cappelenite...... 200 Bementite...... 40,197,256,259 Caracolite...... 52,269 Benitoite...... 189 Carborundum=moissanite...... 112,192 Beraunite...... 46,231 Carmimte...... 233 Bertrandite...... 254 Carnallite...... 206 Beryl...... 195,198 Carnegieite...... 245 Beryllonite...... 248 Carnotite...... 52,273 Berzeliite...... 43,177 Carpholite...... 257 Betaflte...... 46,179 Carphcsiderite...... 53,201 Beudantite...... 47,202,274 Caryinite...... 53,231 Bieberite...... 47,243 Caryocerite (altered)...... 53,177 Bilinite...... 279 Carycplite...... 53 Bindheimite.-...... 47,179,281 Cassiteri' e...... 191 Biotite...... 196,250 Castanite= quetenite (?)...... 53- Bisbeeite...... 48,217 Catapleiite...... 215 Bischofite...... 208 Catoptrite...... 235' Bismite...... 48,202 CeboUite...... 215. Bismutite...... 48,182,183,275,276,282 Celadonite...... 54,257 Bismutosphaerite...... 49,202 Celestite...... 218. Bityite...... 256 Celsian...... 214 Blende=sphalerite...... 184 Cenosite...... 54,262. Bloedite...... 243 Central illumination for measuring indices of Blomstrandine...... 181 refraction...... 14 Blomstrandine group...... 176-183 (passim) Cerargyrite...... 181. Blue vitriol=chalcanthite...... 55,247 Cerite...... 54,233 Bobierite...... 49,209 Cerusite...... 275. Bol&te...... 49,202 Cervantite...... 54 Boothite...... 206 Chabazite...... 185,192,207 Boracite...... 222 Chalcanthite...... 55,247 Borax...... 242 Chalcedony...... 279 Boric acid=sassolite...... 130,241 Chalcodite= stilpnomelane...... 138. Borickite...... 49,175,176 Chalcolamprite...... 55,179" Bort=diamond...... 184 Chalcomenite...... 55,267 Botryogen...... 211 Chalcophanite...... 56,204,267 Boussingaultite...... 53,205 Chalcophyllite...... 197 Bowlingite...... 249 Chalcosiderite...... 56,271 Brackebuschite...... 50,239 Chenevixite...... 5fi, 2SI Bragite=fergusonite...... 74,181,182 Chiastolite=andalusHe...... 258 Brandisite...... 50,260 Childrenite...... 57, 262 Brandtite...... 50,227 Chiolite...... 192 Brannerite...... 51,183 Chloraluminite...... 254 Brewsterite...... 205 Chlorite group... 187-200,213-216.2-19-270 (passim) Brochantite...... 51,269 Bromcarnallite...... 211 Chloritoid...... 230- Bromlite...... 261 Chlormanganokalite...... 188 Bromyrite...... 183 Chlorocalcite...... 245- Bronrite...... 224 Chloromagnesite...... 57.198 Brookite...... 240 Chloropal=ncntronite...... 57 Brucite...... 187 Chcndrarsenite= sarkin ite...... 130,270- Brugnatellite...... 51,194 Chondrodite...... 57,217,221 Brashite...... 211,248 Chrcme clinochlcre...... 214 Bunsenite...... 183 Chromite...... 57,181,182 Bytownite...... 250 Chrysoberyl...... 230 C. Chrysocolla...... ?5,253,280 Chrysolite= oil vine...... 224 Cabrerite...... 51,259 Cacoxenite...... 51,187 Chrysotile...... 2U Calamine...... 217 Churchite...... 58, 188,217 Calcioferrite...... 52,195 Cimolite (doubtful clay)...... 58 Calciovolborthite...... 237 Cinnabar...... 192 Calcite...... 198 Cirrolite, near kaolinite(?). Caledonite...-...... 52,272 Claudetite...... 58,235 California State Mining Bureau, acknowledg­ Clevelandite=albi1e...... 210 ments...... S,34 Clinochlrre...... 214 Callainrte (doubtful). Clinoclasite...... 58,272 INDEX. 287

Page. Page. Clinoenstatite...... 220 Delessite...... 255 Clinohedrite...... 58,261 Delorenzite, near polycrase...... 122,176 Clinohumite...... 222 Demantoid, variety of andradite...... 40,179 Clinozoisite...... 227,228,266 Derbylite...... 67,191,210 Clintonite or brittle mica group..,. 228,230,258,260 Descloizite...... 67,238,277 Cobalt chalcanthite...... 59,248 Desmine=stilbite...... 2-13 Coeruleolactite...... 59,187 Destinezite...... 67,218 Colemanite...... 215 Dewalquite= ardcnnito...... :.. 232,233,235,236 Coleraiuite...... 187 Deweylite, variety of serpentine -...... 133 Collophanite...... 174,175 Diabandtite...... 67,2£2 Collyrite, near halloysite...... 59 Diadochite...... 67,175 Columbite...... 59,282 Diallage=diopside...... 223,221 Conichalcite...... 60,189,231 Diamond...... 184 Cormarite...... 60,195 Diaspore...... 227 Comiellite...... 189 Dickinsonite...... 68,221 Cookeite...... 60,214 Didymolite...... 241 Copiapite...... 61,02,210,211,212,248 Dietrichite...... 68,207 Copperas=melanterite...... 206 Dietzeite...... 6$, 272 Coquimbite...... 186 Dihydrite...... 68,230,269 Cordierite-- - -...... 247,249,253 Diopside...... 223,224 Cordylite...... 200 Dioptase...... 189,220 Corkite...... 63,202,273 Dipyre=mizzonite...... 194 Cornuite...... 174 Dispersion of bisectrices.'...... 20 Corundum...... 200,269 of optic axes...... 45 Cosayrite=enigmatitc-...... 71,233 Disthene=cyanite...... 266 Cotunnite...... 237 Distribution of minerals with regard to op­ Covellite...... 185 tical character, indices of refraction, and Crandallite...... 195 birefringence...... 28 Crecdite...... 212 Dixenite...... 190 Crestmorite...... 280 Dolerophanite...... 281 CristobaUte...... 172,192 Dolomite...... 198,199 Crocidolite--...... 63,226 Douglasite...... 69,isr> Crocoite...... 63,239 Dravite...... 196 Cronstedtite...... 63,200,270 Dufrenite...... 69,234,271 Crossite...... 64,261 Dufrenoysite...... '...... 70,283 Cryolite...... 205 Dumortierite...... 70,203 Cryolithionite-...... 171 Duparc and Pearce, reference...... 10 Cryophyllita...... 251 Durangite...... 70,2S1 Cryptohalite...... 171 Durdenite...... 70,274 Cryptolite= leverrierite (?)...... 174, Dysanalite...... 71,183,239 193,198,245,247,251,254 Crystal system, determination of...... 27 E. Ctunengeite...... 202 Cummingtonite...... 257 Eakle, A. S., acknowledgment...... 8 Cuprite...... 184 Eakleite...... 214 Cuprodescloizite...... 64,276,277 Ecdemite...... 71,203 Cuprotungstite-...... 64,282 Echellite...... 211 Cuspidine...... 64,215 Ectropite...... 280 Custerite-...... 215 Ediugtonite...... 248 Cyanite...... 266 Eglestonite...... 71,184,283 Cyanochroite...... 207 Eichwaldite=jeremejevite...... 197,258 Cyanotricliite...... 65,217 Elbaite...... 197 Cymophane= chrysoberyl...... 230 Eleolite=nephelite...... 194 Cyprusitc= jarosite (?)...... 65 Eleonorite=beraunite...... 46,231 Elpidite...... 213 D. Embedding method of measuring indices of Dahllite...... 196 refraction...... 12 Danalite...... 65,177 Embolite...... :...... 182 Danburite...... 257 Emmonsite...... 71,275 Daphnite...... 66,197,259 Endlichite...... 71,203 Darapskite...... 66,242 Enigmatite...... 71,233 Datolite...... 259 Enstatite...... 220,222 Daubreeite...... 66,281 Eosphorite...... 72,260 Daviesite-...... 66,230 Epidesmine...... 243 Davyne...... 186 Epididymite...... 249 Dawsomte...... 66,247 Epidote...... 26S 288 INDEX.

Page. G. Page. Epidotegroup ...... 176,177 Gadolinite...... 77,178,226,231 226-230 (passim), 266-271 (passim) Gageite...... 78,267 Epistilbite...... 244 Gahnite...... 178 Epistolito...... 72,259 Ganomalite...... 78,190,235 Epsomite...... 241 Ganophyllite...... 267 Equeiite...... 176 Garnet group...... 176-180 (passim) Erinite...... 72,272 Garnierite...... 175,215 Erionite...... 72,205 Gaylussite...... 245 Erythrite...... 72,221,281 Gearksutite...... 78,241 Erythrosiderite...... 262 Gedrite...... 257 Eschynite...... 72,183 Gehlenite...... 198,199 Ettringite...... 73,193 Geijer, Per, acknowledgment...... '.... 8 Euchroite...... 73,225 Geikielite...... 78,203 Euclase...... 220 Genthite, near garnierite...... 175,215 Eucolite...... 196 Georceixite...... 188,218 Eucryptite...... 73,194 Georgiadesite...... 237 Eudialyte...... 18S Gerhardtite...... 265 Eudidymite...... 211 Gibbsitel...... 78,213 Eulytite...... 73,181,202 Gilespite...... 1% Euxenite...... 73,181,182,183 Gilpinite...... 79,215,253 Evansite...... 172 Giobertite=magnesite(?)...... 199 Gismondite...... 247 F. Gladstone and Dale, law of...... 30 Glaserite=aphthitalite...... 186 Facellite=kaliophilite...... 95,193 Glauberite...... 246 Fairfieldite...... 74,219 Glaucochroite...... 266 Faratsihite...... 74,249 Glauconite...... 256 Fafrington, 0. C., acknowledgment...... 8 Glaucophane...... 258 Faujasite...... 172,1S5,207 Glockerite...... 80,281 Fayalite...... 273 Gmelinite...... 185,192,207,242 Feldspar group...... 210-214,245-251 (passim) Goethite...... : ...... 80,276,277 Felsoebanyite...... 74,209 Gonnardite...... 81,209 Ferberite...... 74,2S2 Goslarite...... 81,242 Fergusonite...... 74,181,182 Gothite= goethite...... 80,276,277 Fermorite...... 198 Goyazite...... 82,188 Fernandinite...... 74.282 Graftonite...... 81,227 Ferrierite...... 20B Grandidierite...... 257 Ferrinatrite...... 187 Gratacap, L. P., acknowledgment...... 8 Ferritungstite...... 71,200 Greenockite...... 191 Ferrocolumbite...... 75,277 Grifflthite...... 249 Fibroferrite...... 75,186.211 Griphite...... 81,175 Fibrolite=sillimanite...... 219,221 Grossularite...... 177 Fiedlerite...... 275 Grothine...... 212 Field Museum of Natural History, acknowl­ Groth-Jackson, reference...... 10 edgments...... 8,35 Gruenerite...... 264,267 Fillowite...... 75,223 Guarinite=hiortdahlite...... 82,225 Fischerite= wavellite...... 75 Gummite...... 175 Flinkite...... 75,233 Gymnite, variety of serpentine...... 133,211 Flokite...... 279 Gypsum...... 209 Florencite...... 76,189 Gyrolite...... 194 Fluellite...... 76,207 Fluocerite ...... 76,147,188,196 . H. Fluorite= fluorspar...... 171 Hackmanite...... 172 Ford, W. E., acknowledgment...... 8 Haidingerite...... 82,215 Forsterite...... 76,220,221 Hainite...... 226 Fouqueite= clinozoisite...... 227,228,266 Halite...... 174 Francolite...... 196,255 Halloysite...... 172,173,174 Franklinite...... ,...... 76,184 Halotrichite...... 243 Fremontite...... 76,215 Hambergite...... 215 Friedelite...... 77,198,259 Hamilton, F. McN., acknowledgment...... 8 Frieseite...... 283 Hamlinite=goyazite...... 82 Fuchsite...... 77,253 Hancocldte...... 82,271 Fuggerite, near gehlenite...... :.... 198,199 Hanksite...... 192 Fundamental optical constants...... 9 Hannayite...... 83,250 INDEX. 289

Pago. Page. Hardystonite...... 198 Hydrocerusito...... 202 Harmotomo...... 208 Hydrocyanite...... 281 Harstigite...... 224 Hydrofranktinite= chalcophanitc...... 56,204,267 Harvard University, acknowledgments...... 8,34 Hydrogiobertite, not homogencous(?)...... 89 Hastingsite...... 263 Hydromagnesite...... SO, 210 HatchCttitc...... 183,210 Hydronephelito...... 185 Hatchettolitc...... 83,180 Hydrophilite...... 89,173 Hauerite...... 83,184 Hydrotalcite...... 90,193 Hausmannitc...... 83,203 Hydrotalcite group...... 193-195 (passim) Hautcfeuillitc...... 209 Hydrozincite...... 90,267 Haiiynite...... 173 Hypersthene...... 265 Hayesine=ulexite (?)...... 148,208 I. Hebronite=amblygonilc...... 253 Ice...... 185 Hedenbergite...... 229 Iddings, J. P., Reference...... 9 Hcintzite=hintzcito...... 210 Iddingsite...... 90,227,268 Hcliophyllite=ecdemito...... 71,203 Idocrase= vesuviam'te...... 189,199,266 Hellandite...... 219 Dileite=copiapite...... 62 Helvite...... 177 Ilesite...... 2791 Hemafibrite...... 83,235 Ilmenit e...... 28$ Hematite...... 204 Hcmatolitc...... 83,199 Ilvaite...... 91,273; Hcmatostibiite, near manganostibiite...... 104,273 Immersion media, desirable quality of...... 14- Hemimorphite= calamine...... 217 list of...... 15 Hercynite...... 83,178 stability of...... 16 Herderite...... 255 Immersion method, advantages...... 6 Herrengrundite...... 84,259 Index of refraction, distribution of minerals Hess, Frank L., acknowledgment...... 35 with regard to...... 28 Hessonite...... 178 measurement of, in embedding media.... 20 Hetaerolite...... 84,203 relation between density, chemical com­ Heterosite...... 84,273 position, and...... 30 Heulaiidite...... 208 Indices of refraction, measurement of all..... 22 Hewettite...... 276 methods of measuring...... 12 Hibbenite, near hopeito ...... 85 Inesite...... 91,257 Hibschite...... 176 Inyoite...... 92,244 Hielmite...... 85,191 lodobromite...... 182 Hieratite...... 171 lodyrite.-...... 92,191 Higgensite...... 85,271 Iolite=cordierite...... 247,2-19,253 Hillebrandite...... 255 Iron-copper chalcanthite...... 92,247 Hinsdalite...... 223 Isoclasite...... 92,213 Hintzcite...... 210 Ivaarite...... 180 Hiortdahlite...... 225 J. Hisingerite...... 85,173,175,279 Jadeite...... 220 Hodgkinsonite...... 85,207 Janosite=copiapite...... 62 Hoernesite...... 86,213 Jarosite...... 65,92,152,201,271 Hoegbomite...... 201 Jefferisite...... 93,194,241 Hohmannite=amarantitc(?)...... 39,254 Jeffersonite...... 93,225,229 Homilite...... 86,175,227 Jeremejevite...... 197,258 Homilite (altered)...... 218,219,222 Jezekite...... 251 Hopcite...... 87,251,252 Johannite...... 94,281 Hornblende...... 258,262 Johannsen, Albert, reference...... 10,20 Horn silver=cerargyrite...... 181 Johnstrupite...... 94,222 Hortonolite...... 270 Johns Hopkins University, acknowledgment. 8,34 Howlite...... 87,254 Huebnerite...... 87,237 K. Huegelite...... 87,235 Kaersutite...... 264,266 Humboltine...... 212 Kainite...... 94,241 Humite...... 88,218 Kalicinite...... 242 Humite group...... 217,221,222 Kalinite...... 94,241 Hureaulite...... 88,259 Kaliophilite...... 95,193 Hussakite=xenotime...... 189 Kaolinite...... 249 Hutchinsonite-...... 278 Kehoeite...... 95,174 Hyalophane...... 247 Keilhauite...... 95,236 Hyalotekite...... 88,236 Kentrolite...... 95,237 Hydrargillite= gibbsite...... 78,213 Kermesite...... 96,240 Hydroboracite-...... 86,211 Kieserite...... 211 12097° 21 Bull. 679 19 290 IJTDEX.

Fagev. Kleinite...... 96,191,275> Lorefctoite...... ^.__.._. 203' KnebeUte...... 96,271 Lossenlte...... __,.. 102,231 Knopite...... 90,183 Lotrite...... 222 Knoxvillite= chromium-bearing copiapite. - - 96 Lucinite...... _._.. 102,251 Koechlinite...... 96,277 Ludlamite...... __.. 102,223 Koettigite...... 06,224 Ludwigite...... _,... 234 Kolk, Van der, reference...... 5 Luenburgite...... n-~.. 103,247 Koninckite...... 07,176,280 Koppite...... 97,182 M. Kornerupine...... 262 MackintosMte...... ,~ 103,178 Kremersite...... 281 Magnesioferrite...... 184 Kroehnkite...... 251 Magnesioludwigite...... 102^ 103; 234 Kupfferite.. r ...... 214 Magnesite...... 199 Kyanite=cyanite...... 266 Malachite...... 103; 272 Malacon...... 179 L. MaUardite...... 279 Labradorite...... 213 Manandonite...... 214 Lacroix, A., acknowledgment...... 8 Manganese=chalcanthite...... 244 Lacroixite...... 280 Manganite...... 104;238 Lagonite...... 97,175 Manganosite...... 104; 182 Lanarkite...... 97,274 Manganostibiite...... 104,273 Langbanite...... 97,203 Manganotantalite...... 238 Langbeinite...... '...... 174 Margarite...... 104,258 -Langite...... 97,269 Margarosanite...... 105,269 Lansfordite...... 206 Marialite...... 194 Lanthanite...... 98,252 Mariposite...... 105,256 Larderellite...... 98,209 Marshite...... 184 Laubanite...... 99,185 Martinite...... 105,216 Laumontite...... 245 Mascagnite...... 209 Laurionite...... 275 Massicot...... 105,240 Lautarite...... 99,233 Matlockite...... 107,203,275 Lavenite...... 268 Mazapilite= arseniosderite...... 42,201,202,273 Lawrencite...... 99,195 Meerschaum...... 173 Lawsonite...... 223 Meionite...... 195 Lazulite...... 257 Melanite...... 180 Lazurite...... 173 Melanocerite...... 107,178,199 Leadhillite...... 99,274 Melanophlogite...... 107,172 Lecontite...... 99,241 Melanotekite...... 108,237 Leiflte...... 186 Melanterite...... 206 Leonite...... 243 MeliUte...... 197 Lepidocrocite...... 237,276 Melilite group...... 188,197-199 (passim)' Lepidolite...... 253 Meliphamte...... 196,255. Lepidomelane...... 99,197,258 Mellite...... m Leucite...... 173,186,209 Mendipite...... 108,23& Leucochalcite...... 100,233 Mendozite...... 108,192,241 Leucophanite...... 253 Merwin, H. E., acknowledgments...... 6,18,20 Leucophoenicite...... 100,269 reference...... 16 Leucosphenite...... 100,221 Merwimte...... 227 Leverrierite...... 174,193,196,245,247,251,254 Mesitite...... 109,200 Levynite...... 100,193 Mesolite...... 208 Lewisite...... 100,182 Messelite...... 109,220 Libethenite...... 100,268 Metabrushite=brushite ...... 109,211,248 Liebigite= uranothallite(?)...... 101 Metahewettite...... 275 Lime...... 179 Metavoltaite= metavoltine...... 109,195 Limonite...... 181 Meyerhoflerite...... 110,246 Linarite...... 271 Miargyrite...... 110,240 Lindackerite...... 101,221 Mica group...... 196,197,250-263 (passim) Liroconite...... 101,259 Sec also Clintonite or brittle mica group. Liskcardite...... 101,223 Microchemical tests...... 27 Litharge...... 101,105,204 | Microcline...... 245 LithiophiUte...... 224 Microlite...... 110,179 LMngstonite...... 101,278 Microsommite...... 186 Loeweite...... 193 Miersite...... 110,183 Loewigite...... 101,280 Milarite...... 110,193,246 Lorandite...... 102,240 | Miloschite...... 248 Lorenzenite...... 230 Mimetite...... 110,203,275 INDEX. 291

Page. Minasragrite...... 110,246 Octahedrite= anatase...... 204 Minimum deviation method for measuring Odontolite= turquoise...... 217 indices of refraction...... 21 Okenite...... 245,248 Minium...... Ill,282 Oldhamite...... 182 Mirabilite...... Ill,241 Oligoclasc...... 247 Misenite...... Ill, 206 Olivenite...... 116,231,233,270 Mixite...... 111,189,229 Olivine...... 224 Mizzonite...... 194 Olivine group...... 220-224,261-272 (passim) Moissanite...... 112,192 Opal...... 171,172 Molengraaffite...... 229 Optical character, determination of...... 25 Molybdite...... 112,229,230,232 distribution of minerals with regard to.. 28 Molybdophyllite...... 200 Optical constants, interrelations of...... 10 Molysite...... 281 Orientation, optical...... 26 Monazite...... 232 Orientite...... 231 Monetite...... 112,209 Orpiment...... 117,240 Monimolite...... 183 Orthoclase...... 245 Montanite...... 112,275 Ottrelite...... 228 Montebrazite...... 255 Oxainmite...... 117,248 Monticellite...... 261 Ozocerite= ozokerite...... 117,186 Montmorillonite...... 113 Montroydite...... 113,240 P. Mordenite...... 113,205 Pachnohte...... 205 Morenosite...... 243 Palache, Charles, acknowledgment...... 9 Morinite...... 250 Palaite...... 117,260 Mosandrite...... 219 Palmerite...... 200 Mosesite...... 113,181 Pandermite=priceite...... 122,252 Muscovite...... 252 Paraffin...... 117,186 Paragonite...... 254 N. Parahopeite...... 117,218 Nadorite...... 113,239 Paraluminite...... 118,241 Naegite...... 114,179 Parasepiolite...... 244 NantoMte...... 114,180 Pargasite...... 217 Narsarsukite...... 187 Parisite...... 189 Nasonite...... 114,190 Partschinite= spessartite...... 118 National Museum of Natural History, Stock­ Pascoite...... 271 holm, acknowledgment...... 35 Pectolite...... 118,216 Natroalunite...... 114,187 Peganite...... 118,251 Natrochalcite...... 221 Penfieldite...... 118,191 Natrodavyne...... 186 Penninite...... 187,195,213,250 Natrojarosite...... 114,201,271 Percylite...... 118,180 Natrolite...... 207 Periclase...... 177 Natron...... 114,241 Perofskite, perovskite...... 184,239,277 Natrophilito...... 115,223 Petalite...... 209 Neotantalite...... 115,180 Pharmacolite...... 252 Neotocite...... 115,172,174 Pharmacosiderite...... 118,176,223,225,263 Nephelite (nepheliue)...... 194 Phcnacite, phenakite...... 189> Nepouite...... !...... 256 Phillips, A. H., acknowledgment...... & Neptunite...... !...... ,... 115,225 PhUlipsite...... 207,209,21S Nesquehonite...... 244 Phlogopite...... 255. Newberyite...... 115,209 Phoenicochroite...... 119,285 Newtonite...... 115,187 Pholidolite...... 119,194,247 T Niter...... 244 Phosgenite...... 191,259> Nitrobarite...... 174 Phosphuranylite...... 119,26S Nitrocalcite...... 116,243 Pickeringite...... 119,242 Nitroglauberite...... 116,243 Picotite...... 119,181 Nitromagnesite...... 116,244 Picromerite...... 205 Nocerite...... 116,193 Picropharmacolite...... 120,219 Nontronite...... 57,217, 251, 252,255, 258,259 Picrotephroite...... 26f> Nordenskioeldine...... 200 Piedmontite...... 120,228,230 Northupite...... 173 Pigeonite...... 225 Noselite (nosean)...... 173 Pilbarite...... 120,177 PinaMolite...... 120, 274 O. Pinnoite...... 187 Oblique illumination for measuring indices Piperine and iodides, embedding media..... 16 of refraction...... 13 indices of refraction of mixtures...... 17 Ochrolite...... 282 Pirssonite...... 209 292 INDEX.

Page. Pisanite...... 120,206 Rhagite...... 282 Pittieite...... 121,175 Rhodizite...... 176 Plancheite...... '.. 121,189 Rhodochrosite.. L ...... 201 Planerite...... 173 Rhodolite...... 177 Plattnerite...... 121,203 Rhodonite...... 126,228,268 Plazolite...... 176 Rhomboclase...... 212 Pleonaste...... 83,178 Richterite...... :..... 257 Plumbogummite...... 121,189 Ridgway, Robert, reference...... 41 Plumbojarosite...... 121,201,272 Riebeckite...... 224,264 Podolite...... 280 Rinkite...... 222 PoUucite...... 173 Rinneite...... 188 Polybasite...... 122,278 Ripidolite...... 127,214 Polycrase...... 122,176 Risorite...... 127,181 Polyhalite...... 249 Rivaite (doubtful)...... 127,248 Polymignlte...... 122,183 Riversidite...... 280 Potash alum...... '...... 95,171 Roebling, W. A., acknowledgments...... 8,34 Powellite...... 122,190 Roeblingite...... 127,219 Prehnite...... 218 Roemerite=romerite...... 127,249 Priceite...... 122,252 Roepperite...... 128,270 Princeton University, acknowledgments.... 8,34 Rogers, A. F., reference...... 5 Prisms, preparation of, for measuring indices Romeite (romeine)...... 128,179,281 of refraction...... 21 Roscherite...... 256 Prochlorite...... 123,216 Roscoelite...... 263 Prolectite...... 222 Roselite...... 128,227 Prosopite...... 123,208 Rosenbusch (Wiilflng), reference...... 10 Proustite...... 204 Rosenbuschite...... 128,224 Pseudoboleite...... 202 Rosieresite...... 173 Pseudobrookite...... 123,239 Rowlandite...... 129,177 Pseudomalachite= dihydrite...... 68,230,269 Rumpflte...... 129,187,214 Pseudomesolite...... 208 Rutherfordine...... 129,281 Psittacinite=cuprodescloizite...... 64,276,277 Rutile...... 192 Ptilolite...... 242 Pucherite...... 123,277 S. Purpurite...... 124,234,236 Sachs, A., reference...... 39 Pyrargyrite...... 204 Salmiac (sal ammoniac)...... 176 Pyreneite...... 229 Salmoite...... 135 Pyroaurite...... 124,195 Salmonsite...... 129,221 Pyrobelonite...... 277 Samarskite...... 129,183 Pyrochlore...... 124,180 Samiresite...... 130,180 Pyrochroite...... 199 Saponite...... 130,194 Pyromorphite...... 202,275 Sapphirine...... 265 Pyrope...... 176,177 Sarcolite...... 188,219 Pyrophanite...... 204 Sarcopside...... 281 Pyrophyllite...... 124,242 Sarkinite...... 130,270 Pyrosmalite...... 124,198 Sartorite...... 283 Pyrostilpnite...... 240 Sassolite...... 130,241 Pyroxene group...... 220-230,256-269 (passim) Scacchite...... 174 Pyroxmangite...... 230 Scapolite group...... 194,195 Pyrrhite=koppite(?)...... 125 Schaller, W. T., acknowledgments...... 7,35 Scheelite...... 190 Q. Schizolite...... 130,219 Quartz...... 186 Schneebergite...... 130,181,282 Quenstedtitei=copiapite(?)...... 61 Schorlite...... 198 Quetenite...... 53,125,210 Schorlomite...... 130,180 SchroecMngerite...... 131,263 R. Schroetterite (clay mineral)...... 131,175 Raimondite (doubtful)...... 125 Schwartzembergite...... 132,203,277 Ralstonite...... 171,279 Scolecite...... 245 Raspite...... 125,238 Scorodite...... 132,231,232,233 Realgar...... 126,278 Searlesite...... 245,246 Reddingite...... 126,221 Selenium and arsenic selenide, embedding Refraction, total...... 20 media...... 20 Refractive energies, specific...... 31 Sellaite...... 185 Remingtonite...... 126,200 Senaite...... 133,204 Retzian...... 126,232 Senarmontite...... 181,237 Rhabdophanite...... 126,189 Sepiolite...... 245 INDEX. 293

T. Page. Serendibite...... 226 Tachhydrite...... 193 Serpentine group...... 133,175,211,215,244,249 Tagilite...... 140,271 Serpierite...... 133,258 Talc...... 252 Seybertite...... 260 Tamarugite...... 141,207 ShattucMte...... 133,231 Tantalite...... 59,238 Sheridanite...... 213 Tapiolite...... 141,191 Sicklerite...... 134,267 Taramellite...... 141,231 Siderite...... 201 Tarapacaite...... 268 Sideronatrite...... 134,210 Tarbuttite...... 141,265 Siderotil...... 134,247 Tavistockite...... 142,210 Sillimanite...... 219,221 Taylorite...... 142,205 Sipylite...... 134,181 Tellurite...... 142,237,276 .Smithite...... 134,278 Tellurium and arsenic selenid'e, embedding .Smithsonite...... 200 media...... 20 Sodalite...... 172 Tengerite...... 142,213 Soda niter...... 195 Tennantite...... 142,184 .Sodium bicarbonate...... 134 Tenorite...... 142,283 Soumansite...... 187,212 Tephroite...... 143,270 Spadaite...... 135,174 Terlinguaite...... 143,278 .Spangolite...... 199 Termierite...... 171 Specific refractive energies, table of...... 31 Teschemacherite...... 246 Spencerite...... 135,254 Tetrahedrite...... 143,184 Spessartite...... 178 Thalenite...... 267 Sphaerite...... 135,250 Thaumasite...... 193 Sphaerocobaltite...... 135,201 Thenardite...... 143,206 Sphalerite...... 184 Thermonatrite...... 143,244 Spinel group...... 177-184 (passim) Thomsenolite...... 241 Spodiosite...... 136,223 Thomsonite...... 208 Spodumene...... 222 Thorianite...... 143,182 Spurrite...... 262 Thorite...... 144,176,190 Staurolite...... 229 Thortveitite...... 269 Stellerite...... 243 Thuringite...... 258 Stercorite...... 205 Tilasite...... 260 Stevensite...... 173 Titanite...... 235 Stewartite...... 260 Titanolivine...... 223 Stibiconite...... 136,175,176,178,179,180,281 Toernebohmite...... 234 Stibicolombite...... 239 Topaz...... 217 Stibiotantalite...... 239 Torbernite...... 195,217,253,255 Stibnite...... 278 Tourmaline...... 198 Stichtite...... 194 Trechmannite...... 144,234 Stilbite...... 243 Tremolite...... 255 Stilpnomelane...... 138,199,200,263,270 Trichalcite...... 144,263 Stokesite...... 217 Tridymite...... 206 Stolzite...... 138,203 Trigonite...... 282 Strengite...... 138,227,229,265 Trimerite...... 266 Strigovite...... 139,261 Triphylite.-,...... 225,264 Strontianite...... 261 Triplite .f^...... Wl,22S Strueverite...... 139,191,204 Triploidite...... 145,228 Struvite...... 207 Trippkeite...... 145,190 Succinite...... 174 Tripuhyite...... 145,237 Sulphatic cancrinite...... 193 Tritomite...... 145,177 .Sulphoborite...... 247 Troegeritc...... 145,196,256 Sulphohalite...... 139,171 Trona...... 146,243 Sulphur...... 237 Tscheffkinitc...... 146,179,180,273,276 Sulphur and selenium, embedding media, Tschermigitc...... 172 preparation of...... 18 Tsumebite...... 147,235 index of refraction of mixture...... 19 Tungstite...... 147,276 Sussexite...... 140,211 Turgite...... 147,277 Svabite...... 140,199 Turquoise...... 217 Svanbergite,...... 188 Tychite...... 173 Sylvite...... 173 Tyrolite...... 147,266 Symplesito...... 140,261 Tysonitc= fluocerite...... 147,188,196 Synadelphite...... 140,234 Tyuyamunite...... 148,272,273 Syngenite...... 245 U. Szaibelyitc...... 197 Uhligite...... '... 182 Szmikite...... 140,215 Ulexite...... 148,208 Date Due

294 INDEX.

Page. Page.. United States National Museum, acknowl­ Wellsite...... 157,208; edgments...... 8,34 Wernerite...... "...... 195 University of California, acknowledgments.. 8,34 Wherry, E. T., acknowledgments...... 7,8 University of Stockholm, acknowledgment.. 35 Whewellite...... : 212 Uraconite...... 149,232 Wiildte...... '.. 157,180 Uranochalcite...... 149,220 Wilkeite...... 197 Uranocircite...... 149,255 WiUemite...... '...... 189' Uranophane (uranolite?)...... 149,261 Winchell, A. N. and N. H., references...... 5,9 Uranopilite...... 150,218 Witherite...... 262 Uranospathitc...... 245 Woehlerite...... 265 Uranosphaerite...... 150,236 Wolframite...... 157,239 Uranospinite...... 150,195,251 WoUastonite...... 256 Uranothallite...... 151,208 Wright, F. E., acknowledgment...... 7 Urbanite...... 152,225 Wright, F. E., references...... '. 10,12,13 Ussingite...... 209 Wolfenite...... 203 Utahite= jarosite(?)...... 152,201,271 Wulfing, references...... 35 Uvanite...... 234 Wurtzite...... 191 Uvarovite...... 179 X. V. Xanthoconite...... 278 Valentinite...... 152,277 Xanthophyllite...... '...... 260 Vanadinite...... 203 Xanthosiderite (doubtful). Vanthoffite...... 243 Xenotime...... 189 Variscite...... 152,212 Vashegyite...... 153,173,279 Vauquelinite...... 153,276 Vegasite...... 189 Yale University, acknowledgments...... 8,34 Velardenite...... 198 Yttrialite...... 157,177 Vesuvianite...... 189,199,266 Yttrocerite...... 158,171 Veszelyite...... 153,221 Yttrocrasite...... 158,181 Vilateite...... 268 Yttrofluorite...... 172: Villiaumite...... 171,192 Yttrotantalite...... 158,181 Viridine...... 223 Z. Vivianite...... 153,216 Zaratite...... 1.58,174,175 < Voelckerite...... 153,197 Zebedassite...... 279 < Voglitc...... 154,211 Zeolite group. 172,185-193,205-213,242-248 (passim) Volborthite...... 154,236,274 ZeophyUite...... 194 Volchonskoite...... 251 Zepharovichite ...... 158,279 Voltaite...... 155,175 Zeunerite...... 158,197' Voltzite...... 155,191 Zincaluminite...... 159,193 Vrbaite...... 283 Zinc-copper chalcanthite...... 246 W. melanterite...... 207 Wagnerite...... 213 Zincite...... 159,191 Walpurgite...... 155,274 Zrnkosite...... 159,261 Wapplerite...... 156,210 Zinnwaldite...... 254' WarwicMte...... 156,233 Zippeite...... 159,263,265. Water...... 171 Zircon...... 190,236 Wattevillite...... 156,241 Zirkelite...... 160,182' WaveUite...... 156,211 Zoisite...... 226- Weinschenk-Clark, reference...... 9 Zunyite...... 160,175

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