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JOHNS HOPKINS UNIVERSITY CI RCULARS Publis/ied wit/i t/ze approbation ofthe Board of Trustees VoL. YIIJ.—No. 75.1 BALTIMORE, SEPTEMBER, 1889. [PRICE, 10 CENTS. SCIENTIFIC NOTES. Contributions to the Mineralogy of Maryland. By II. Mica Schist. No new minerals. It is doubtful whether all the schists of the Baltimore area are not sufficiently feldspathic to be regarded as GEORGE H. WILLIAMS. gneisses. Since the publication of the “Notes on the Minerals occurring in the III. Crystalline Limestone. In addition to the species, calcite, phlogo- Neighborhood of Baltimore” in 1887, a number of additions have been pite, brown tourmaline, tremolite, pyrite, and iron hydroxide, already made to our knowledge of mineral occurrences both in this district and in recorded as occurring in the crystalline limestones and dolomites of Balti- more distant parts of the State. I have therefore thought it worth while more county, we may now enumerate the following: Quartz, very common to publish a preliminary record of the principal of these, which may serve in rounded grey nodules known to the quarrymen as “flint;” much rarer as an appendix to the above-mentioned pamphlet. in well-formed limpid crystals. Mr. Tidy, for many years salesman for the I shall mention first the new minerals found within the Baltimore Beaver Dam marble company, told me of a remarkable druse of quartz neighborhood—the 625 square miles embraced within the limits of the crystals accidentally found by the breaking of a marble step. He described University Field Club map, to which alone reference was made in the the crystals as resembling tbe glass prisms frequently suspended from chan- “Notes “—and subsequently speak of such species a.s have come to my notice deliers. Orthoclase. This is the Necronite (“ fetid feldspar”) of Dr. Hay- from other parts of Maryland. den (Am. Jour. Sci. (I) Vol. I, p. 306, 1819), and is common at Texas and Literature. In addition to the published papers on the local mineralogy in the Mine Bank limestone belt, between Summerfield and Notch Cliff. of Maryland formerly known to me, I may record the following: Dr. Horace Green Mica. A bright green variety of muscovite, not chromiferous, is not Hayden’s “Geological Sketch of Baltimore” was published in Vol. I of infrequently encountered at the Texas quarries. Green Pyrozene. Large, the Baltimore Medical and Philosophical Journal, and that portion of it but imperfect crystals of a pale green to greyish white pyroxdne have been referring to the occurrence of chromite in the Bare Hills was reprinted in furnished me from the Texas limestone by Mr. Horace Burrough, of the Bruce’s American Mineralogical Journal, Vol. I, 1813, pp. 243—248. In University. These crystals have the prismatic angles, cleavage, and basal 1813, Robert Gilmor, Jr. published a “Descriptive Catalogue of Minerals parting of pyroxene, and are probably malacolite, though no analysis has occurring in the vicinity ofBaltimore, arranged according to the ‘distribution as yet been made of them. Similar greyish green pyroxene is mentioned m~thodique’ of H~uy” (Bruce’s Am. Mi Journal,Vol. 1, pp. 221—233). He by Tyson as abundant at Texas (bc. cit.). Associated with the malacolite enumerates 35 distinct species. In 1830 appeared Philip Tyson’s “Locali- given me by Mr. Burrough are small but sharp and glistening crystals of ties of Minerals near Baltimore,” with an appendix by C. U. Shepard (Am. sphene. Pink Scapolite. In several specimens of the coarse-grained lime- Jour. Sci. (I) Vol. 18, p. 78). Seven years later the same writer published stone of Texas (the so-called “alum-stone” of the quarrymen) brought me a “Descriptive Catalogue of the Principal Minerals of the State of Mary- by Mr. Burrough are good-sized, though imperfectly developed, crystals of land” (Trans. Maryl. Ac. Sci., Vol. I, Pt. 1,1837, pp. 102—117). Many pale rose colored scapolite. The best ofthese measure 4 cm. in length, and other references to the occurrence of particular minerals within the limits 6—9 mm. in diameter. Their prismatic zone is well developed and allows of the State are scattered through the earlier numbers of the American of measurement, but their terminations are imperfect. The mineral was Journal of Science and other scientific periodicals. determined to be scapolite by crystallographic and optical tests. The angles Minerals of the Baltimore region. The following species have been identi- all show a quadratic symmetry, while the interference figure, refractive fied within the past two years in each of the eight formations, mentioned in index, double refraction and negative character all agree with this species. the “Notes” as occurring inside the area of the Field Club map. The planes of the crystals possess that peculiar glazed appearance so char- I. Gneiss. In addition to garnet, kyanite, and fibrolite as accessory con- acteristic of silicates occurring in limestone. Black Tourmaline was also stituents in the highly micaceous gneiss, staurolite, in large black crystals noticed in one specimen of very micaceous limestone from Baltimore county. frequently twinned and particularly prominent on weathered surfaces, has Butile, in small dark red crystals with a high metallic lustre, is mentioned been found near Owings’ Mills; on Western Run, east of Ashland Furnace; by. Tyson as not uncommon at Texas, and it has been found by me in the and at Warren’s Mills, on the Gunpowder river. In a microscopic section similar limestone near Meredith’s Bridge. Serpentine was found quite abun- of gneiss from the immediate contact with the gabbro at Hollofield’s Sta- dantly at the Texas quarries, appearing to have resulted from the alteration tion, staurolite was discovered where it may possibly have resulted from the of the greenish pyroxene. The Graphite mentioned by Tyson as occurring contact action of the igneous rock. In association with the zeolites occur- at the same locality has not yet been identified. ringin the gneiss of the Jones Falls quarries, calcite, as perfectly crystallized IV. Eruptive Granite. The statement was made two years ago that no as the best Iceland spar, was found by Mr. Maurice Straus. accessory minerals were known in the eruptive granites of Woodstock and JOHNS HOPKINS 100 [No. 75. Ellicott city. Since then Dr. W. H. Hobbs has shown that these rocks are unusually interesting from the fact that they contain a constant proportion As in the former list, italics indicate the occurrence of fair cabinet speci- of allanite (orthite) surrounded by a parallel growth of epidote (vid. Univer- mens; an asterisk, that the mineral has been chemically analyzed. sity Circulars, No. 65, p. 69, April, 1888). It has provedimpossible to isolate Mineralsfrom other localities in Maryland. The most interesting mineral sufficient of the former mineral for analysis, though its optical behavior discovery which has been recently made in Maryland is that of the chro- places its nature beyond doubt. The surrounding epidote was however mium tourmaline and the chromium muscovite ~fuchsite) found near the old analyzed by Mr. W. F. Hillebrand, of the U. S. Geological Survey, with the chrome pits near Etchison P. 0., Montgomery county. These are described following result: in detail in the following communication by Mr. A. C. Gill, and therefore 5i0 need no further mention here. 2 37.63 The occurrence of another mineral new to Maryland is worthy of record, A1203 20.86 (by difference). especially on account of its geological significance. This is ottrelite, which Fe2O3 15.29 I have found abundantly disseminated through certain of the phyllites at MuO .31 the old copper mine on Dolyhyde Creek, one mile east of the village of CaO 22.93 Liberty in Frederick county. The rock is a perfectly cleaved purple slate, M90 .31 spotted throughout with small dark green plates, which rarely exceed a H20 2.23 millimeter in diameter. These sometimes exhibit an approximately hex~ P205 .44 agonal outline, and are arranged nearly perpendicular to the cleavage planes 100.00 of the rock. They are very hard, have a perfect basal cleavage and a glistening lustre as seen with a hand lens. Under the microscope cleavage One crystal of allanite, with its exterior zone of epidote, collected by Mr. plates show a marked pleochroism, h (~ a) being olive green and b (~ Is) a Gill at the granite quarries near Woodstock, measures nearly five milli- dark bluish green. The optical an0le is large and the optical character meters in length.* I have also observed sharp and glistening crystals of negative. In a thin section of the rock cut parallel to its cleavage, the spheae and cubes ofpyrite in the Woodstock granite. ottrelite crystals appear as lath-shaped individuals, four to six times as long V. Gabbro. No new minerals have been observed in the gabbro, but as they are wide, and with the cleavage lines following their lou0 direction. Mr. Gill has noticed dodecahedral garnets, nearly an inch in diameter, in The extinction is plainly oblique to this cleavage, on an average as much the gabbro-diorite 1~ miles west of Pikesville Station. In the gabbro-diorite as 150. All individuals are twinned according to Tschermak’s law, two from Ilchester, Dr. W. H. Hobbs found rutile which, together with the superposed plates showing their oblique extinction in reverse directions. ilmenite, was surrounded by an alteration rim identical with that described In such sections, the color of the ray vibrating parallel to the vertical by von Lasauli as titanomorphite. (See University Circulars, No. 65, p. 69, axis, 6 ( a), is seen to be pale yellow. The crystal plates are frequently April, 1888). united into radiating groups. No distinct instances of zonal structure were VI. Serpentine. Crystallized magnesite occurs in the serpentine at “Sol- observed.

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