Fall 1986 Gems & Gemology

VOLUME XXII FALL 1986

The quarterly journal of the Gemological Institute of America FALL 1986 Volume 22 Number 3

TABLE OF CONTENTS

EDITORIAL 129 Tucson '87: Don't Miss It! Richard T Licldicoat, fr.

FEATURE 130 A Simple Procedure to Separate Natural from Synthetic Amethyst on the ARTICLES Basis of Twinning Robert Crowningshield, Cornelius Hurlbut, and C. W Fryer Pink Topaz from Pakistan Edward Gubelin, Giorgio Graziani, and A. H. Kuzmi Carbon Dioxide Fluid Inclusions as Proof of Natural-Colored Corundum fohn 1. Koivula Contributions to a History of Gemology: Specific Gravity -Origins and Development of the Hydrostatic Method fohn Sinkankas

NOTES 166 Colombage-Ara Scheelite AND NEW Mahinda Gunawardene TECHNIQUES

REGULAR 170 Gem Trade Lab Notes FEATURES 177 Editorial Forum 178 Book Reviews 180 Abstracts 187 Gem News

ABOUT THE COVER: Recently a small hillock near Katlang, Pakistan, has begun to produce fine gem-quality pink topaz. Authors Edword Gubelin, Giorgio Giaziani, and A. H. Kazmi present an in-depth report on topaz from the Ghundao hill, the only known in-situ deposit of pink topaz in the world today. The finest-quality Pakistan pink topaz is reminiscent of the stones shown here. This necklace and the n~atchingearrings represent more than 200 ct of fine pink topaz. The set is said to have been commissioned by King George 111 in 1795, and the stones are presumed to have originated in Russia. Photo * 1984 Harold el Erica Van Pelt-Photogra- phers, Los Angeles, CA. Jewelry courtesy Gary R. Hansen, Precious Gemstones, St. Louis, MO.

Typesetting for Gems &. Gemology is by Scientific Composition, Los Angeles, CA. Color separa- tions are by Effective Graphics, Compton, CA. Printing is by Waverly Press, Easton, MD.

EDITORIAL Editor-in-Chief Editor Editor, Gem Trade Lab Notes STAFF Richard T. Liddicoat, Jr. Alice S. Keller C. W. Fryer Associate Editors 1660 Stewart St. Editor, Gemological Abstracts Santa Monica, CA 90404 Peter C. Keller Dona M. Dirlam D. Vincent Manson Telephone: (213) 829-299 1 John Sinkankas Assistant Editor Editor, Book Reviews Jeffrey M. Burbank Technical Editor Sally A. Thomas Carol M. Stockton Subscriptions Contributing Editor and Janet M. Fryer, Manager Editor, Gem News Lisa Hebenstreit, Assistant Manager John I. Koivula

PRODUCTION Art Director Production Assistant Production Assistant STAFF Linda Manion Cecile Miranda Patricia Mayer

EDITORIAL William E. Boyajian Robert C. Kammerling Sallie Morton REVIEW BOARD Santa Monica, CA Santa Monica, CA San lose, CA Robert Crowningshield Anthony R. Karnpf Kurt Nassau New York, NY Los Angeles, CA Bernardsville, N1 Pete Dunn Robert E. Kane Ray Page Washington, DC Los Angeles, CA Santa Monica, CA Dennis Foltz John Koivula George Rossman Santa Monica, CA Santa Monica, CA Pasadena, CA Chuck Fryer Henry 0. A. Meyer James E. Shigley Santa Monica, CA West LaFayette. Indiana Santa Monica, CA C. S. Hurlbut, Jr. Cambridge, MA

SUBSCRIPTIONS Subscriptions in the U.S.A. are priced as follows: $29.50 for one year (4 issues), $82.50 for three years (12 issues), Subscriptions sent elsewhere are $40.00 for one year, $115.00 for three years. Special annual subscription rates are available for all students actively involved in a GIA program: $24.50 U.S.A., $35.00 elsewhere. Your student number must be listed at the time your subscription is entered. Single issues may bepurchasedfor $8.00in the U.S.A., $1 1 .OOclscwhere.Discounts arcgiven for bulkordersof 1001more of any one issue. A limited number of back issues of G&G are also available for purchase. Please address all inquiries regarding subscriptions and the purchase of single copies or back issues to the Subscriptions Manager.

MANUSCRIPT Gems 01 Gemology welcomes the submission of articles on all aspects of the field. Please see the Suggestions for Au- SUBMISSIONS thors in the Summer 1986 issue of the journal, or contact the editor for a copy. Letters on articles published in Gems e) Gemology and other relevant matters are also welcome.

COPYRIGHT Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. copyright law for private use of patrons. Instructors are permitted to photocopy isolated articles for noncommercial AND REPRINT classroom use without fee. For other copying, reprint, or republication permission, please contact the Editor. PERMISSIONS Gems a) Gemology is published quarterly by the Gen~ologicalInstitute of America, a nonprofit educational organization for the jewelry industry, 1660 Stewart St., Santa Monica, CA 90404. Postmaster: Return undeliverable copies of Gems eJ Gemology to 1660 Stewart St., Santa Monica, CA 90404. TUCSON '87: DON'T MISS IT!

1,126-ct "padparadscha" sapphire crystal, a superb 667-ct emerald crystal from A Muzo, the first tourmalines from Afghanistan, large quantities of aquamarine from Nigeria, many pounds of natural-color and dyed lapis lazuli, carats upon carats of treated blue topaz and synthetic (as well as natural) amethyst, emerald, ruby, and the like. Jeremejevite, parisite, taaffeite, cat's-eye opal, color-change garnet. The new, the rare, the unusual, and hundreds of thousands of carats of the better-known gemstones in a full range of qualities and colors. This is Tucson. That is, these are some of the items seen in recent years at the Tucson "show," really a multitude of gem and mineral shows and related activities that dominate the city of Tucson, Arizona, every February.

Ever since the mineral- and gem-collecting and lapidary hobbies started to gain in popularity a quarter of a century ago, a number of shows have been developed in various cities in Europe and the United States. In the U.S., those in Detroit, Pasadena, and Miami, among others, attracted significant numbers early on, but the one started by the Tucson Gem and Mineral Society in 1955 has become a unique happening and a must for the serious gem dealer or collector. Although it started as a show for hobbyists and *'$tillretains some elements of the hobby genre, "Tucson" is now one of the most 'important professional displays of gems and the jewelry arts in the world. It attracts top gem dealers, mineral dealers, collectors, and jewelers from every continent. While 'individual dealers have worked out of hotel rooms and lobbies in the area surrounding the convention center for almost two decades, separate "shows" that precede or coincide with the original show are now sponsored by the American Gem Trade Association (AGTA), the Gem and Lapidary Dealers Association (GLDA),and other organizations. During the first two weeks in February (the main shows go from the 6th to the 15th in 1987), thousands of dealers appear in Tucson selling everything from rough geodes off the backs of trucks to sophisticated pieces of jewelry that carry prices as high as six figures. The quantities of tourmaline, topaz, lzunzite, and garnet of all colors and descriptions are mind boggling. Yet it is also the first opportunity for many to see new gem varieties, gems from new localities, and the results of new treatments and synthesis techniques. While for some Tucson is a source of information on price trends and shifts in supply, for others Tucson is the excitement of seeing the newest and the rarest.

Yet Tucson offers even more. The GIA, AGTA, and other organizations sponsor a variety of lectures and short courses during this period. Virtually all of the major gem and mineral publishers are represented, as are many of the jewelry manufacturing and tool suppliers. The Sonora Desert Museum, the scenic countryside, and the many fine hotels and restaurants all serve to make a working trip more pleasant, and the mild Tucson climate is invariably cooperative.

All in all, the Tucson show is one of the really exciting events of the colored-stone enthusiast's year. Our recommendation: Don't miss it! Richard T. Liddicoat, ]r. Editor-in-Chief

Tucson '87 GEMS &. GEMOLOGY Fall 1986 129 A SIMPLE PROCEDURE TO SEPARATE NATURAL FROM SYNTHETIC AMETHYST ON THE BASIS OF TWINNING

By Robert Crowningshield, Cornelius Hurlbzzt, and C. W. Fryer

Dr. Karl Schmetzer recently showed how ince 1970, when synthetic amethyst first became near-flawless to flawless natural amethyst savailable commercially, it has created problems in could be separated from synthetic ame- identification for gemologists. Although inclusions have thyst on the basis of the presence of Brazil proved reliable in distinguishing synthetic from natural in twinning in the natural stones. Whereas most "flawed" amethysts, until recently no test was avail- Dr. Schmetzer's procedure required a spe- able to separate the flawless or near-flawless stones that cial apparatus, the authors have determined that a standard gemological po- represent the bulk of the fine faceted stones on the market lariscopeis more than adequate to make (figure 1).As a result, otherwise ethical jewelers and sup- the separation in most cases. Although pliers everywhere may have unwittingly sold thousands of some synthetic amethyst does show evi- synthetic amethysts that were represented to them as nat- dence of twinning, in the synthetic stones ural. In 1985, however, Dr. Karl Schmetzer described a examined thus far it has taken a form that procedure by which a distinction can be made (see also is distinctly different from the Brazil Schmetzer, 1986).Subsequently, the authors adopted Dr. twinning seen in most natural amethysts. Schmetzer's procedure for use with standard gemological The presence of certain inclusions as well equipment. This test alone is not always unequivocal but, as the nature of the color zoning seen in when used in conjunction with other observations, such as natural versus synthetic amethysts is of color zoning, it presents an excellent method for the sepa- primary use in making a separation. How- ever, where there are no inclusions or color ration of most near-flawless synthetic and natural zoning, the presence of Brazil twinning in amethyst. the natural amethyst will usually make The procedure described by Dr. Schmetzer is based on the distinction. the fact that most natural amethysts are repeatedly twinned on the Brazil law, while synthetic amethysts are usually grown as single crystals (Schneider and Droschel, 1983; Lind et al., 1983).In polarized light, a twinned stone will exhibit varying degrees of interruption in the spectral rings, while an untwinned stone will show undisturbed ABOUT THE AUTHORS rings of spectral colors. While Dr. Schmetzer's description Mr. Crowningshield is a director of the GIA Gem suggested that a special apparatus was required, we have Trade Laboratory in New York City; Dr. Hurlbut is found that a polariscope or standard polarizing microscope professor emeritus 01 mineralogy at Harvard Uni- versity, Cambridge, Massachusetts; and Mr. Fryer is adequate to observe the diagnostic twinning. To confirm is chief gemologist in the Research Department 01 the accuracy of our method, we examined more than 1100 the Gemological Institute of America, Santa natural and 200 synthetic amethysts. In this article, we Monica, California. describe how to apply these simpler procedures. Acknowledgments: The authors would like to thank Mr. Ross Altman, Ross Altman, Inc., and Mr. Paul First, however, it is well to review twinning in ame- Heubert, Inter-Ocean Trade Company, both of thyst as well as why synthetic quartz was made in the first New York, lor the gracious loan of stones lor study. place. Other tests useful in distinguishing natural from 0 1986 Gemological Institute of America synthetic amethyst are also discussed briefly.

130 Identification of Amethyst GEMS & GEMOLOGY Fall 1986 Figure 1. One of the major problems facing gemologists today is the separation of naturalfroni synthetic amethyst, as illustrated by the 9.40-ct natural oval cut and the 5.48-ct synthetic emerald cut shown here. Photo 0Tino Hanimid.

TWINNING IN AMETHYST terminalr or rand 2 faces. The lamellae are alter- The fact that almost all natural amethyst is nately right- and left-handed. They may give rise to twinned according to the Brazil law has been sets of delicate striations, or to open polygonal known for at least 150 years. The optical structure markings on the rhombohedra1 faces, and cause a of amethyst was first described by Sir David rippled, or fingerprint appearance on the fracture Brewsterin 1821 (Frondel, 1962),and was correctly surfaces. The twinning can be studied in etched interpreted as due to the polysynthetic twinning of sections or, more conveniently, by optical means." right- and left-hand quartz. In the course of the The last sentence of the above quotation, if 19th century, further descriptions were given by applied to the study of gemstones, might better many other workers. A brief summary of these and have been written: "The twinning can be studied later works is found in Dana's System of Mineral- in etched sections or more conveniently and less ogy (Frondel, 1962): "Amethyst virtually always destructively by optical means." For etching is shows polysynthetic twinning on the Brazil law. done with hydrofluoric acid, a harsh treatment of a Untwinned crystals have been noted. The twin gem. The twin lamellae are, however, made read- lamellae, a fraction of a millimeter thick, are re- ily apparent by the process (figure 2). markably uniform and are arranged parallel to the Gemologists are familiar with the term poly-

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 131 synthetic twinning in connection with the re- amethysts have been observed, they were probably peated twinning of corundum and some feldspars. cut from the area completely under the minor In the termpolysynthetic, "synthetic" is not to be rhombohedron. confused with its use meaning "man-made," but rather carries the classical meaning of "put to- THE HISTORICAL DEVELOPMENT OF gether;" while "poly-" is a combining form mean- SYNTHETIC AMETHYST ing "many." Thus, the term polysynthetic con- Before World War 11, Brazil was able to supply the veys the meaning of "many thin crystals (lamellae) world with the rock crystal necessary to make the put together." oscillators used to control radio frequency. Since Quartz is optically active; that is, if polarized the oscillator must be free of twinning, the first light moves parallel to the optic axis, the plane of step in manufacture was to inspect the raw crys- polarization is rotated. The rotation is to the right, tals for Brazil twinning. This was done in an im- conventionally clockwise, in right-hand crystals mersion tank, using a giant polariscope with polar- and to the left in left-hand crystals. The shorter the izers one foot square. The hand-held quartz crystal wavelength, the greater is the rotation; violet light was turned until the optic axis was parallel to the is thus rotated more than red light. As stated in the direction of light through the polariscope and the above quotation from Dana's System of Mineral- Brazil twinning, if present, was observed. Many ogy, Brazil twinning results in alternating lamellae crystals with twinning throughout were discarded, most commonly under faces of the major rhombo- others with little or no twinning were passed on to hedron, r, the large triangular faces that terminate the next operation, cutting. the quartz crystal. Figure 3 is a drawing of a section During the war, however the demand for Bra- perpendicular to the optic axis that shows twin- zilian quartz skyrocketed. In the United States ning under the major rhombohedron with the alone, thousands of tons of quartz crystals were right-hand portions of the quartz shown in white used in the manufacture of over 50 million small and the left-hand portions of the quartz shown in oscillator plates cut at precise crystallographic black. If slices of quartz represented by this draw- angles. In 1944, because quartz was high on the ing were observed between crossed polarizers, they critical list of minerals, the U.S. Signal Corps initi- would take on the appearance seen in figure 4. One ated a quartz synthesis program. Private industry would see narrow parallel bands of alternating also became involved. Although success was not colors and shadow under the major rhombo- achieved until after the war, by 1950 hydrother- hedron~and broad swaths of color under the minor mally grown synthetic quartz was in mass pro- rhombohedrons. duction. Now untwinned quartz crystals grown on With light moving parallel to the optic axis untwinned seed plates supply the material for os- through the twinned areas, the rotation of polari- cillators in radios, watches, cloclzs, radio- zation is alternately right and left. Because the frequency filters, and other apparatus where fre- lamellae are not of exactly the same thickness, the quency control of electrical circuits must be net rotation is always greater in one sense than precise. the other, resulting in different colors for the The successful synthesis of colorless quartz right-hand and left-hand regions. The lamellae are pointed the way to the manufacture (by the irradi- thus striated and sharply defined, whereas the ation of iron-bearing synthetic quartz) of colored untwinned areas are of a single color. Twinning quartz (Balitsky, 1980).But with citrine and ame- may be confined to isolated triangular areas, but thyst so abundant and relatively inexpensive, frequently in amethyst it will be evidenced by there would seem to be no incentive to synthesize straight lines crossing the stone. There may be these materials. Since about 1970, however, both only one set of parallel lines, or there may be two or have been made commercially in the Soviet Union three sets making angles of 60' or 120' with one and, later, in Japan. To date, most synthetic pro- another (again, see figure 4). These latter result duction is untwinned, single-crystal material. from the meeting of the twinned areas under two or three of the rhombohedron faces. DETECTION OF BRAZIL TWINNING In the authors' experience, untwinned crystals WITH THE POLARISCOPE (as noted in the Dana's quotation above) are very It is to Dr. Karl Schmetzer, of the University of rare. Although some natural untwinned faceted Heidelberg, West Germany, that credit must be

132 Identification of Amethyst GEMS &. GEMOLOGY Fall 1986 Figure 2. Etching an amethyst with hydrofluoric acid clearly reveals [he presence of Brazil twinning in these two 18-ct stones. The test is, however, highly destructive and therefore not practical for gemologists. Photo by PShane McClure. given for first promoting (1985)the optical test to useful. Since amethysts tend to be relatively larger differentiate flawless or near-flawless synthetic than more costly stones, we have found small from natural amethyst. However, there is the im- flared colorless glass votive candle holders, about plication by Schmetzer that to observe the twin- two inches (5cm) high and two inches in diameter, ning, one must use an "improved sample holder" to be good immersion cells. They are also sold as with a horizontal immersion microscope. We have oyster cocktail condiment holders for restaurant found that twinning can be equally well observed use. One is shown with a polariscope in figure 5. using a vertical polarizing microscope, but even Various immersion liquids may be used, but the more easily by simply using a standard gemologi- closer the refractive index of the liquid is to that of cal polari$cope with the stone held in ordinary quartz, the better. However, water usually pro- stone tweezers or even in one's fingers. vides relatively good results. In adapting Schmetzer's procedure to the open To observe twinning in amethyst, the stone polariscope, we have used several items that are must be turned so that its optic axis is parallel to readily available. Many times, the twinning effect can be seen without immersion. However, when immersion is necessary, a number of items are Figure 4. The twinning evident in this natural amethyst closely resembles the idealized drawing shown infigure 3. Note the narrow bands of Figure 3. This idealized illustration shows left- color under the major rhombohedrons and the hand (black) and right-hand (white)portions of a broad swaths of color under the minor twinned amethyst. Adaptedfrom Schlossin and rhombohedrons. Magnified 15 X; Lang, 1965. photomicrograph hy Robert Kane.

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 133 Figure 6. The differencebetween the twinned natural (oval) and the untwinned synthetic (emerald cut) amethyst is clearly seen lookingin the optic axis direction of each under crossed polarizers. Photo by David Hargett.

right direction. Another problem, more serious, is that if a natural stone has been cut so that it lies entirely under the minor rhombohedron, it will not exhibit twinning. Sometimes only a small area of the stone encompasses an area under the major Figure 5. A simple polariscope and immersion cell are sufficient to identify Brazil twinning in rhombohedron, but the diagnostic twinning effect, near-flawless to flawless natural amethyst. although minimal, is still conclusive. As quoted Photo by David Hargett. from Dana above, there have also been reported rare untwinned natural amethyst crystals. These could not be detected by the Schmetzer test alone. the line of sight through the polariscope or micro- Of course, mounted stones offer another problem. scope, which must have crossed Polaroids, that is, If the optic axis direction is obscured by the set- the dark position. The basic problem is thus one of ting, they cannot be tested without unmounting. crystallographic orientation. Cut amethysts usu- Herein lie the shortcomings of the test. ally are not oriented except for maximum weight Figure 7 shows the twinning seen with the retention, or best color, so that finding the optic polariscope in a variety of natural stones. Equally axis direction is a challenge. This is the reason Dr. good results can be obtained with a polarizing Schmetzer felt a special holder was necessary. microscope (figure 8). In contrast, figure 9 illus- Only rarely is a stone cut with the table perpen- trates three untwinned synthetic stones. The nat- dicular to the optic axis. Nevertheless, such is the ural stone shown in figure 10 had to be maneu- case with the two stones in figure 6. The oval is a vered quite a bit, as it apparently was cut from natural amethyst showing twinning, whereas the material predominantly under the minor rhombo- emerald cut shows the untwinned effect of a syn- hedron. However, even a tiny area of fine parallel thetic stone. The photograph was taken "dry," colors shows the presence of twinning, and thus that is, the stones were not immersed. given our present knowledge proves natural origin. Rarely in practice will the test yield such con- Some synthetic amethysts, notably from clusive and dramatic results as easily-and with- Japan, do exhibit twinning (Balalzirev et al., 1975). out immersion. For one thing, the optic axis of the However, our observations thus far indicate that stone being tested may coincide with the point of a the twinning in these synthetics has a distinctly fancy shape or the girdle of any stone, making it different appearance from that of natural ame- difficult to maneuver with the tweezers to find the thyst. The twinning in the synthetics appears as

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 figure 7. As these three examples of natural ame- :hyst viewed through a polariscope indicate, the brazil twinning may vary somewhat from one ;tone to the next. Often the stone will have to be maneuvered with the tweezers or in one's fingers 'o see the twinning clearly. While immersion nay be helpful, these photos were all taken with :he stones dry. Photos by Shane McClure.

irregular-shaped, small arrowhead-shaped, or Figure 8. Twinningin natural amethyst can also flame-like areas (figure 11). Such stones will have be identified using a polarizing microscope with definite zones of yellow or dark purple that coin- crossedpolflrizers. Magnified 6x; photo- cide with these flame-like or irregular-shaped micrograph by John Koivula. twinned areas (figure 12).Even in very small areas, however, the acute included angle of the twinning in the synthetics can be distinguished from the 60Â or 120Â°anglecharacteristic of Brazil law twinning in natural amethyst. Citrine that has been produced by heating natural amethyst will behave in the polariscope in the same manner as natural amethyst. Bi-colored quartz, sometimes called "ametrine" or amethyst/citrine (figure 131, usually behaves differ- ently. Koivula (1980)noted that Brazil twinning is present in the amethyst zones, whereas the citrine zones are untwinned (figure 14). Thus, ame-

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 135 Figure 9. These untwinned synthetic amethysts Figure 10. Even a small area of twinning, as provide a striking contrast to their twinnednatu- shown here in rock crystal quartz, indicates nat- ral counterparts when viewed with the polari- ural origin. Photo by David Hargctt. scope. Note the broad color bands that are characteristic of untwinned single-crystal material. Photo by David Hargett. sence of twinning before calling a stone "synthetic." The presence of recognizable inclusions, thyst/citrine and citrine with twinning present such as those described by Giibelin and Koivula can be identified as natural by this method. (19861, proves natural origin. At one time, "fingerprint" inclusions were regarded as proof of natural OTHER EVIDENCE OF NATURAL VS. origin. This is no longer the case since some syn- SYNTHETIC AMETHYST thetic crystals may also have liquid-filled "finger- Since some natural amethyst may be untwinned, print" inclusions (figure 15), especially near the one should consider evidence other than the ab- surface of the crystal. The presence of spicules, or

Figure 11. In the synthetic amethyst manufac- Figure 12. Color zoning coincides with the tured in Japan,a form of twinning appears as flame-like or irregular-shaped twinned area in small irregular-shaped, arrowhead-shaped, or some synthetic amethysts of Japanese manufac- flame-like areas that are very different from the ~ute,as this photo of the stone in figure 11, taken twinning seen in natural amethyst. Magnified without the polarizers, indicates. Magnified 6 X; 6 x; photomicrograph byJohn Koivula. photomicrograph byJohn Koivula.

136 Identification of Amethyst GEMS & GEMOLOGY Fall 1986 Figure 13. This bi-colored-quartzis also known Figure 14. When amethyst/citrine quartz is os "ametrine" or amethyst/citrine. Photo by viewed with a polariscope, the presence of David Hargett. twinning in the amethyst section indicates that the stone is natural. Photo by Shane McClure.

"nailhead," inclusions (observed very rarely) proves hydrothermal synthetic origin. Occasion- The pigmenting of amethyst is associated with ally, portions of the seed crystal will occur in a Brazil twinning, and thus characteristically the synthetic stone and they are highly diagnostic. deepest color lies~nderthe major rhombohedron, They usually appear as a slightly cloudy white or whereas the sections under the minor rhombo- yellowish iglane often peppered with high-relief "breadcrumbs" (figure 16). Although "bread- Figure 16. "Breadcrumb" inclusions, although crumbs" may (very rarely) be found in natural seen (very rarely) in natural amethyst, usually amethyst, a gemologist seeing them in an other- provide a good clue that the host stone is syn- wise flawless, untwinned stone would be well ad- thetic, as shown here in a synthetic amethyst of vised not to call it natural! Japanese manufacture. Magnified 45 X; In the course of this study, 105 natural ame- photomicrograph by David Hargett. thysts were examined with regard to color zoning.

Figure 15. Liquid-filled fingerprint inclusions are now sometimes seen in synthetic amethyst, as shown here, as well as in natural stones. Magni- fied 20 X; photomicrograph by David Hargett.

a ft, /Â

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 137 Figure 18. When color zoningis seen in a synthetic amethyst (here, 10.86 ct), it is limited to Figure 17. This basal section of amethyst clearly darker and lighter shades of purple. Photo by illustrates the deeply pigmented sectors under Shane McClure. the major rhombohedron and the nearly colorless sectors under the minor rhombohedron that are characteristic of color zoning in natural amethyst. Photo by Cornelius Hurlbut. hedron may be colorless or nearly so (figure 17). Even under the major rhombohedron the color may not be uniform. According to Frondel (1962), "The amethyst color may be equally developed in successive twin lamallae, but more often alternate lamellae, either right or left, are selectively pigmented." Color zoning was present in all 105 natural amethysts examined. In a few, zoning was in one Figure 19. The color zoning in natural amethyst direction only, that is, parallel to but one rhombo- (here, 7.04 ct) is typically straight or angular in hedron face. In most, color zoning was parallel to two or three directions, and consists of zones of two or three of the rhombohedron faces from purple and violetish blue or colorless material. which the stones were cut. Brazil twinning was Photo by Shane McClure. present in all but two of the stones. One of these showed color banding parallel to two rhombo- direction of color zoning. But if the zoning is in two hedron faces; the other had color banding parallel or three directions, a natural origin is indicated. It to three. should be noted that the zoning observed in most In the limited number (6)of faceted synthetic synthetic stones is limited to darker and lighter amethysts examined for color zoning, all were un- shades of purple (figure 18);parallel zones of purple twinned. Five were of uniform color throughout, and violetish blue or colorless material and angu- which is rarely if ever seen in natural amethyst lar zoning indicate natural amethyst (see figure (again, see figure 17). One showed imperfect color 191. Other gemologists (e.g., Sondra Francis, pers. zoning parallel to a rhombohedron face that was comm., who has studied this phenomenon in interpreted as being parallel to the seed from depth) report that many synthetic amethysts are which the crystal was grown. In addition to the cut indeed zoned but confirm the zoning differences stones, there was available a piece of synthetic noted above between natural and synthetic stones. rough which included the colorless seed plate cut In recent years, gemological and mineralogical parallel to a rhombohedron face. This was flaw- investigators have noted in print the rippled frac- less, untwinned material with a faint color zoning ture surface of natural amethyst and even outlined parallel to the seed. The observations indicate an a procedure for frosting the surface of an unknown uncertain identity of an untwinned stone with one amethyst (by slight regrinding with fine grit on a

138 Identification of Amethyst GEMS & GEMOLOGY Fall 1986 soft wheel at low speed) so that it is possible to see the complete absence of zoning indicates syn- with the unaided eye the twin lamellae of the thetic origin, but does not provide conclusive proof natural stone [Schneider and Droschel, 1983). Of of origin. Characteristic inclusions can also pro- course, the stone must then be repolished. vide proof of origin. Considerable attention has also been paid in If no other conclusive evidence of origin is Europe to attempts to distinguish amethysts by available, infrared spectrometry appears to contain infrared spectrometry (Katz, 1962; Chakraborty such proof, once the practical aspects of routine and Lehmann, 1978; Zecchini, 1976; and Lind and application have been resolved. Ongoing research Schmetzer, 1983).Problems with specimen orien- in this area promises to solve the few remaining tation, as well as the practical difficulties encoun- difficulties in identifying natural and synthetic tered in transmitting spectral signals through amethyst. However, this study indicates that the faceted gemstones, have thus far thwarted at- overwhelming majority of stones on the market tempts to provide a routine method of identifica- today can be distinguished by the methods already tion through infrared spectra. However, new infra- available. red instrumentation is now available, and results to date are promising for this approach to the separation of natural and synthetic amethyst. REFERENCES CONCLUSION Balakirev V.G., Tsinober L.I., Tsyganov E.M.(1975) Electron microscope study of Brazil twins in synthetic amethysts. While some "experienced" amethyst dealers have Soviet Physical Crystallography, Vol. 19, pp. 517-520. reported no difficulty in separating synthetic ame- Balitsky V.S. (1980)Synthetic amethyst: Its history, methods of growing, morphology, and peculiar features. Zeitscl~riftder thysts from natural stones merely by looking, Deutschen Gemnibfogischen Gesellscl~uft,Vol. 29, pp. others who ,have mastered the "Schmetzer" test 5- 16. have reported that their stock is badly mixed. One Chakraborty P., Lehn~annG. (1978)Distribution of OH in synthetic and natural quartz crystals. Journal of Solid State- dealer stated that even parcels from his own cut- Chemistry, Vol. 17, pp. 305-31 1. ting shops abroad have had as much as 25% syn- Frondel C. (1962)Dana's System of Mineralogy, 7th eel., Vol. 111: thetic amethyst mixed with the natural. It is the Silica Minerals, John Wiley & Sons, New York. Giibelin E. J., Koivula J. I. (19861 Photoatlas of Inclusions in authors' hope that this article will serve to reas- Gemstones. ABC Edition, Zurich. sure the ethical trade that this no longer need be Katz A. (1962)Hydrogen in quartz. Phillips Research Reports, the case, that the practice of salting synthetics into Vol. 17, pp. 133- 135 and 201 -279. parcels of natural stones can be effectively Koivula J.I. (1980) Citrine-amethyst quartz-a gemologically new material. Gems ei) Gemology, Vol. 16, No. 9, pp. deterred. 290-293. Although the reader is reminded that the use of Lind Th., Schmetzer K. (1983) A method for measuring the infrared spectra of faceted gems such as natural and syn- twinning cannot be 100% effective, in preparing thetic amethysts.fourna1 of Gemmology, Vol. 18, No. 5, pp. for this article the authors tested more than 1300 4 11-420. amethysts of known origin [over 1100 natural and Lind Th., Schmetzer K., Bank H. (1983)Untersuchungsmetho- den zur Unterscheidung von natiirlichen und synthetischen 200 synthetic).By noting inclusions, color zoning, Amethysten. Zeitschrift der Deiitschen Gemmologischen and twinning, all the stones could be satisfactorily Gesallschufr, Vol. 32, No. 2/3, pp. 126- 137. identified. Schltjssin H.H., Lang A.R. [1965] A study of repeated twinning, lattice imperfections and impurity distribution in ame- On the basis of information currently avail- thyst. Philosophical Magazine, Vol. 12, pp. 283-296, able, we conclude that the presence of Brazil law Schmetzer K. [I9851 Ein verbesserter Probenhalter und seine twinning in an otherwise flawless amethyst Anwendung auf Problen~eder Unterscheidung natiiralicher und synthetischer Rubine sowie naturlicher und synth- proves natural origin. However, twinning in the etischer Amethyste. Zeitschrift der Deiitschen Gem- form of an acutely angled, flame-like pattern posi- mologischen Gesellschaft, Vol. 34, pp. 30-47. tively identifies synthetic origin. With practice, Schrnetzer K. (1986)An improved sample holder and its use in the distinction of natural and synthetic ruby as well as there should be no confusion between these natural and synthetic amethyst. Journal of Gemmology, twinning patterns. Vol. 20, No. 1, pp. 20-33, In the absence of twinning, synthetic origin is Schneider W.L., Droschel R. (19831Beobachtungen an polysyn- thetisch verzwillingten Quarzen-ein Beitrag zur Unter- probable, but further evidence is required to make scheidung naturlicher und synthetischer Amethyste. a positive identification. Angular or straight zon- Zeitschrift der Deufschen Gemmologischen Gesellscl~uft, ing with colorless or violetish blue zones next to Vol. 32, pp. 28-38. Zecchini P. (1976) fitude de Itabsorption infrarouge de quartz purple areas characterizes natural amethyst. The d'origine naturelle ou de synthese. Revue de Gemmologie presence of zones of only light and dark purple or Association Francaise de Gemmologie, No. 60, pp. 14- 17.

Identification of Amethyst GEMS & GEMOLOGY Fall 1986 139 PINK TOPAZ FROM PAKISTAN By Edward Gu belin, Giorgio Graziani, and A. H. Kazmi

In addition to the relatively recent he occurrence of pink topaz in Pakistan was discov- discovery of significant amounts of emer- Tered less than 20 years ago. This attractive material ald, aquamarine, and ruby, Pakistan (figure 1) has been reported on several occasions in the has also begun to produce fine gem-quai- gemological literature [Afridi et al., 1973; Bank, 1976a and ity pink topaz. In a small hillock of b; Petrov et al.; 1977a, b, and c; Jan, 1979),but details of the recrystallized limestone north of Katlang, narrow calcite veins encase pink topaz deposit itself have only recently become available. In this crystals up to 3 cm long accompanied by article, the authors report on their investigation of the larger amounts of reddish brown, tan, geology and mineralogy of the pink topaz deposit near and colorless topaz crystals. More than Katlang, and on the chemistry and the gemologically 70,000 ct of gem-quality pink topaz ascertainable properties of this material. As part of this has been reported to date. The refractive study, the authors also investigated the other color vari- indices, optic axial angle, unit-cell eties of topaz found at the deposit and their reaction to dimensions, and density of the topaz treatment. are influenced by a partial replacement of fluorine by hydroxyl ions. The color is LOCATION AND ACCESS due to trace elements -principally The topaz is found in one of two hills that rise abruptly chromium (Cr3+). Treatment experiments revealed that the color of the brown, from the fertile agricultural plain of the Mardan District in tan, and colorless topaz from this source the neighborhood of a small village. This settlement of may be improved by irradiation and heat. farmers and the topaz hillock both bear the same name- Ghundao-and are located about 4 lzm (2.5 mi.) north of the small town of Katlang (figure 2). The geographic coordinates of the topaz-bearing hill of Ghundao are latitude 34Â¡24'N longitude 72Â¡06'E which places it about ABOUT THE AUTHORS 63 km (40 mi.) northeast of Peshawar and about 20 km Dr. Gubelin, a prominent gemologist and north of the district capital Mardan "as the crow flies" author, is from Meggen, Switzerland; Dr. Graziani (approximately 50 km southeast of the Swat Valley emer- is professor of earth sciences at the University ald deposits; see Gubelin, 1982).The hill is easily reached of Rome; and Dr. Kazmi, formerly technical director of the Gemstone Corporation of Pakistan, by automobile. The other hill, which contains no topaz is currently deputy director general of the Geolog- deposits, lies about 1 lzm northwest of the Ghundao hill. ical Survey of Pakistan. The summit of Ghundao, the topaz hill, is approximately Acknowledgments: The authors wish to extend 80 m higher than the village, and the two hills are their gratitude to the many people who contributed to this study and especially to Brigadier conspicuous features of an otherwise unbroken plain Kaleem ur Rahman Mirza, of the Gemstone (figure 3). Corporation of Pakistan, for his lively interest in the outcome of this study and for his generous GEOLOGY AND OCCURRENCE cooperation. Manuscript received February 13, 1984; revised manuscript received May 30, The Ghundao hill, only about 340 x 275 m at its base, is 1986. composed primarily of strata of gray recrystallized lime- @ 1986 Gemological Institute of America stones tilted to a near-vertical orientation, and intercalated

140 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 with phyllites and autoclastic limestone breccias irregularly dispersed, dust-like bituminous (figure 4). There are three main lithologic units in inclusions. the hill: These rocks have been grouped by previous 1. Light gray, thick-bedded, largely autoclastic workers (Martin et al., 1962; Afridi et al., 1973; limestone. Jan, 1979) with the lower Swat-Buner Schistose 2. Dark gray, medium-bedded, fine-to-medium Group, and are believed to be of Silurian-Devonian grained crystalline limestone; the lower part age (Afridi et al., 1973, Jan, 1979). The algal is composed of algal structures. This unit structure in the limestone and the gastropod also contains some quartz, mica, and altered fossils found in the lower beds of the Ghundao hill pyrite crystals. support this assessment of age. The Ghundao 3. Thin-bedded limestone and calcareous limestones are probably a northern extension of shale. The gray color of the rock is caused by the Silurian-Devonian rocks of Nowshera forma-

Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 141 tion (which could be about 400 million years old), (figure 6). These veins are interspersed by although they may comprise a different deposi- milky-white quartz, green muscovite, and tional facies. green talc, as well as by minor amounts of a Structurally, the Ghundao hill comprises a limonitized clay-like material. Topaz miner- "mini" anticlinorium with the axes of the tight alization is mainly confined to this latter folds trending east-west and plunging eastward type of calcite vein. The veins appear to (figures 4 and 5).The limbs of the larger folds have completely penetrate the hill conformably themselves been tightly drag-folded and exten- with the gray limestone strata. sively faulted. The gray limestone has been in- truded in places by veins of coarse-grained white .The topaz mineralization is structurally con- calcite and quartz. These veins, in which the topaz trolled (figures 5 and 6) and forms typical saddle- is found, are of two types: reef type structures in the limonitized clay-like muscovite accumulations of the larger type 2 veins 1. Short, narrow irregular veins (several centi- described above. At several places, the limestone meters wide and less than a meter long) of has been invaded by stockworks of calcite and fine-grained white calcite, which cut ran- quartz veins which also contain beautiful, per- domly across the strike of the fold axes. fectly euhedral crystals of quartz and topaz, usu- 2. Much larger veins (as much as 2 m-6 ft. - ally completely embedded in the calcite, but wide and several meters long) of coarser- occasionally found protruding into cavities or grained calcite, which occur along fault crevices, or lying loose in the breccia debris planes that run parallel to the fold axes (figure 7).

Figure 2. This map shows the location of the topaz hill at Ghundao, in the Mardan District of Pakistan, and the geological setting of the surrounding area. Artwork by Cecile Miranda.

Jnconsolidated Sediments .Quaternary) Shewa Garhi Granite Â(Eocene) Ambela Granite (Cretaceous) Kot Pranghar Melange Complex rn (Cretaceous) ILower Swat Buner Schistose Group (Paleozoic) Granite/Granite Gneiss -(Cambrian)

142 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 Figure 3. The view from the Ghundao hill across the plain of Katlang toward the southeastern foothills of the Hindu Kush range shows how flat the plain from which the two hillocks rise actually is.

Figure 4. An open cut in th flank of Topaz Hi11 reveal the vertical stacking of th strata, South North

100 feet -30.5 meters

Fault

Thin-bedded limestone and shale

Figure 5. This diagramatic geological section across the Ghundao hill shows the three major lithologic units and the extensive folding and faulting. After A.H. 1Zazmi. Artwork by Cecile Miranda,

A "pinch and swell" structure is common along into later-formed vein calcite. Although Jan men- the topaz-bearing calcite veins, although some are tions that the mineralizing solutions for the Kat- quite narrow (type 1) and others are much larger lang topaz may have been genetically related to the and more extensive (type 2). Topaz also occurs in Swat granite gneisses, the authors believe that the calcite that forms small lenticular tension gashes Katlang topaz is late syntectonic, and was formed in limestone at the crests of the folds or drag folds largely through pneumatolytic processes linked (again, see figure 6). with the final stages of consolidation of the much Jan (1979) concluded that the topaz may have younger (Eocene) granitic intrusions of Shewa, formed by hydrothermal/pneumatolytic activity, which are in close proximity to the topaz deposits followed by tectonic movements which fractured (again, see figure 2). Some supporting evidence is the crystals and resulted in their incorporation provided by the fact that trace-element analyses of

Figure 6. This diagram illustrates the structure and mineralization of the topaz deposit at Ghundao. Note especially the topaz-bearing calcite veins and tension gashes, After A. H.Kazmi. Artwork by Cecile Miranda.

144 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 Warsalz and Shewa granites (from the Peshawar basin] by Kempe (1983) show up to 10 ppm chromium. This may explain the presence of Cr203 in the Katlang topaz (see below). Study of these granites by Chaudhry and Shams (1983)has revealed that these rocks developed in an environ- ment that would have been ideal for the formation of the type of mineral deposits that we see today at Katlang.

Figure 7. Although the pink topaz from Ghundao usually occurs embedded in the host calcite, it is also found as fine, well-formed Figure 8. Miners collect the loose rocks at the crystals protruding from the host calcite into a bottom of one of the large open cuts that has vug or as loose crystals. been blasted into the side of the Ghundao hill. One miner uses a pick to remove pieces of calcite from the wall of the cut. MINING AND PRODUCTION Topaz was first discovered at Ghundao in the fall of 1972 by local residents who dug the crystals tinued unauthorized mining during this period, secretly and then brought them to the market in until the GEMCP began geologic exploration and Peshawar. When the government became aware of systematic mining of the deposits in 1981. This this illegal digging, the West Pakistan Industrial work was carried out under the guidance and Development Corporation (WPIDC)was asked to supervision of one of the authors, Dr. Kazmi. undertake detailed studies of the topaz-bearing Presently, all mining in the area is under the hillock. The Mineral Development Cell of the control of the GEMCP All workings are open cuts WPIDC in Peshawar first studied the Ghundao hill consisting of trench-like incisions (figure 81 in January 1973 (Afridi et al., 1973). Prospecting blasted into the calcite veins that are known to rights were held by the WPIDC and later by its bear topaz. Hand tools as well as pneumatic drills successor, the Palzistan Mineral Development Cor- are used to dislodge fragments of calcite that poration (PMDC), but no systematic mining was remain attached to the open-cut walls. To mini- conducted until the deposits were talzen over by mize damage to the crystals during mining, great the Gemstone Corporation of Palzistan (GEMCP] care is talzen in deciding where to drill, in using in 1979. Local residents, however, reportedly con- low-strength explosive charges, and in controlling

Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 145 Figure 9. On a heap of blasted pieces of rock, miners break promising pieces in search of topaz crystals. the blasting. Promising lumps of rock are then easily by hand to the small depot in Ghundao carefully broken up with hammers to free the Village. Only a very small percentage of the enclosed topaz crystals (figure 9). crystals are clean enough to be cut as gems. By February 1983 (when the senior author The total production of gem-quality pink topaz visited Ghundao in the company of Dr. Kazmi), recorded up to November 1984 is 72,076 ct. An- three open cuts had been driven deep into the nual production currently ranges between 20,000 hillside; the largest of these cuts almost reached and 30,000 ct; collectors' specimens are also avail- the summit. At the time, approximately 15 miners able. The largest cut pink topaz from this source were working the deposit. The daily production of recorded to date is 37.76 ct (illustrated in Spengler, topaz was so small that all of it could be carried 1985, p. 669).

Figure 10. These three crystals represent the main colors - colorless, pink, and brownish - of the topaz found at Ghundao. The sizes of the three crystals are somewhat representative of the proportion in which these colors occur at Ghundao (the largest crystal is approximately 10.25 mm). Like most of the topaz found at this localitx these crystals are highly fractured and broken.

146 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 Figure 11. These three faceted pink topazes from Ghundao illustrate the most prized color found at the locality (from left to right: 5.68 ct, 18.41 ct, 9.38 ct).

4, v CRYSTALLOGRAPHY the pink gems find ready buyers in the gem well-developed euhedral crystals of topaz are rare market; unfortunately, these represent a small at this locality; the majority are broken and highly proportion of the total production. This deposit fractured (see figure 10). Individual crystals sel- near Katlang is the only known in-situ occurrence dom attain a length of 3 cm and are usually stubby of pinlz topaz. Although some pinlz crystals were to tabular in habit; that is, they are flattened along once found in the gravels in the Sanarlza River (also the a-axis due to the pronounced development of called the Kamenlzo River; see Kornetova, 1950)in the prism {l lo}. Well-crystallized specimens dis- the Ural Mountains of the USSR, the in-situ play the four bipyramids {011}, {012}, {l1 l}, and deposits yielding them have never been found. All {112} and two to three prisms of {llo}, {120}, and other pink topazes - especially those from Brazil {010}. Both {llo} and {120} are nearly always well - owe their color to heat treatment. formed and are commonly striated. The basal The pink hue of the Pakistan material is so dis- pinacoid {OOl} is rarely present; when it is present, tinctive that the color-trained eye can distinguish it is usually etched. Most crystals are heavily it without much difficulty from the "burned" included. specimens mentioned above. The prized shade of Unit-cell parameters were obtained from X-ray Katlang pink topaz is faintly violet in tone, and the powder diffraction data, indexed by comparison best examples can be described as cyclamen pink with the data listed by the JCPDS file No. 12-765 (figure 11).This shade is comparable to color tones and using a least-squares refinement program 10:2:2 with corresponding values Xn44.4; Yc34.6; (Applemen and Evans, 1973) with reagent grade and Zc37.5 of DIN Color Chart 6164. NaCl as an internal standard. The unit-cell pa- The pink topazes from Katlang take an excel- rameters determined are: 3 = 8.3841 Â 0.0013; b lent polish and therefore reflect a lively surface = 8.8335 ? 0.0009; = 4.6617 Â 0.0006 A; V = brilliance (i.e., luster). They are slippery to the 3.45 Â 0.1 A3. touch, as is usual with faceted topazes. VISUAL APPEARANCE PHYSICAL PROPERTIES The topaz crystals found at Ghundao range from To establish the physical constants, five faceted colorless through very pale beige to light brown, to gems (2.5-18.4 ct) and seven cleavage fragments very pale to deep pink (again, see figure 10).Only were tested using standard gemological instru-

Pink Topaz from Pakistan GEMS & GEMOLOGY Fall I986 147 TABLE 1. Gemological properties of topaz from Katlang, Pakistan.3

Property Pink Colorless Brownish

Refractive indices na = 1.629-1.631 (1.630) na = 1.610-1.612 (1,611) na = 1.608-1.61 1 (1.610) np = 1.631-1.634 (1.632) np=1,612-1.615 (1.614) np=1.611-1.614 (1.613) n-y = 1.638-1.642 (1,640) n-y = 1.620-1.623 (1.622) IT/ = 1.617-1.621 (1.619) Birefringence + 0.009-0.01 1 (0.010) + 0,010-0.011 (0.010) +O.OOS-0.010 (0.009) Axial angle 2V = 53'00' 2V = 53'04' 2V = 56O10' Pleochroism n-y = yellow none Very weak; colorless, yellowish, brownish np = purple (mostly pale) n-y = dense mauve to violet Absorption Extremely weak line at 682 nm none none (indicates coloration by Cr^) Luminescence Very weak; dark red to long-wave none none ultraviolet radiation, Distinct to brilliant milky green sheen (amplified in fractures) to short-wave ultraviolet radiation Density 3.51-3.53 gIcm3 (3.52) 3.55 g/cm3

"The extreme values of constants are given, with mean values in parentheses. Twelve pink stones and three each of the colorless and brownish topazes were examined. ments (table 1). The data obtained concur very basal plane, either gas or liquid filled or as attrac- closely with the published statements of Bank tively patterned healing fissures (figure 12). The (1976a and b), Jan (1979),and Petrov (1977). most interesting patterns are made by various two- In comparison to the other color varieties found phase - liquid and gas - inclusions, in which the at Ghundao, the pink stones are outstanding not liquid phase is dominant. The peculiar shapes of only for their high refractive indices, but also for these inclusions did not allow for quantitative their somewhat low density, as Bank remarked analysis, but observations with the microscope (1976a and b). indicated that they consist of aqueous solutions of medium to low salinity, since daughter crystals INCLUSIONS were not observed. When the liquid phase Fissures constitute the bulk of the inclusions in moistens the walls of the fissures in little drops or the faceted pink topazes, while mineral inclusions in elongated tubes in parallel alignment, the regu- apparently are quite rare. These fissures often lar, planar dispersion makes it easy to recognize appear as cleavage cracks running parallel to the the host gem because the pattern is similar to that of innumerable topazes from widely separated Figure 12. Discrete two-phase inclusions in parallel arrangement are commonly Figure 13. These parallel rows of two- seen in pink topaz from the Ghundao hill, phase inclusions are a diagnostic internal near Katlang, Pakistan. Magnified 50 x . feature of topaz. Magnified 16 x .

148 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 Figure 14. These fine fibers of two-phase Figure 15. These curious swirl marks inclusions seen in pink topaz from Ghundao and growth features observed in Ghundao are reminiscent of the trichites normally topaz appear to be connected to cleavage found in tourmaline. Magnified 20 x , cracks. Such cracks in parallel alignment are an indication that these topazes should be treated with care. Magnified 30 x . sources (figure 13). However, when the liquid inclusions are irregularly dispersed and entwined lilze tangled threads, they look exactly lilze the well-known trichites in tourmaline (figure 14). The correlation between physical properties Also noteworthy in this material are random and the weight percentage of fluorine was studied swirls which seem to be connected with the by Ribbe and Rogenberg (1971), Bambauer et al. parallel cleavage fissures (figure 15).Cleavages and (1971),and others. The substitution of the fluorine their accompanying swirl marks also occur in ion by the larger hydroxyl group leads to an otherwise internally flawless pinlz topazes. increase in the refractive indices. At the same time, there is a lessening of the optic axial angle CHEMISTRY 2Vy and of the density. The behavior of the pink The composition of topaz is fairly constant except topazes from Katlang is consistent with these for variation in hydroxyl content. Several micro- observations. probe analyses were carried out on each of three Chemical analyses were not carried out on the different samples, which represented three differ- colorless or brown Katlang topazes. However, it ent shades of cyclamen pinlz. Wet chemical analyses were subsequently performed, using a specific ion electrode for determining the amount of fluo- TABLE 2. Wet chemical analysis of pink topaz from rine (table 2). Particular care was taken to avoid Pakistan. fluorine loss in the process of fusing the sample Numbers of ions on the basis with alkaline carbonates. Because of problems Oxide Wt. % of 24 (0, OH, F) encountered in performing the thermogravimetric Si02 determination of H20present in the sample, total Ti02 H20 was estimated after heating at a constant A12Â° temperature of 850Â° for 24 hours. The analyzed croo3 v205 topazes reveal a low Fe content and minor amounts FeOa of Cr, y and Ca, while Mg and Mn are present in MnO some of the samples but not in others. The analy- MgO CaO ses also indicate that the pinlz topaz from this F source is poor in fluorine and rich in hydroxyl H20+ b (considering that topaz may accommodate as H^O -13 much as 30 wt.% F). The systematic variation of unit-cell dimensions with respect to F and OH concentrations (Rosenberg, 1967; Chau'dhry and Total 100.69 Howie, 1970; Ribbe and Rosenberg, 1971; Bam- "Total iron as Fed. bauer et al., 1971) allow us to estimate a fluorine bDetermined by thermogravirnetry. content of 15.6-16.3 Â0.5 wt.% .

Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 149 can be deduced from the physical properties (table and brownish specimens which the senior author 1) - i.e., their lower refractive indices and higher had obtained in Pakistan. All irradiation experi- specific gravities compared to the pink variety - ments were conducted using 20 Mrad gamma rays that they are richer in fluorine. Indeed, the median from a cobalt-60 source; all heat treatments lasted values for fluorine may be assessed at about 21 Â 1 15 hours. The results are shown in figure 16. wt%. Sample 1. Reddish brown; lost its orange compo- TREATMENT AND COLOR nent after 15 hours heated at 500Â°Cacquiring a pale pink hue. When it was subsequently irradi- The attractive pink color of topaz is caused by ated, turned orange-brown; did not change color trace amounts of the Cr3+ ion; other topaz colors when heated to 250Âor 300Â°Cheating to 350Â° are due to color centers (Nassau, 1984).In accord, caused a change back to pink (figure 16, top row). microprobe analyses of the Katlang pink topazes Conclusion: The pink color is due to Cr; it is showed chromium-oxide contents of 0.01 to 0.03 probably stable at any temperature. The orange- wt.% that correlate with the intensity of color. No brown color is induced by Cr plus a color center color change was observed in specimens that had produced by irradiation; it is probably not affected been exposed to the hot summer sun of Peshawar by daylight, but will turn pink if subsequently (38'-48OC) for 65 days (Jan, 1979). heated to 350Â° for 15 hours. Given the occurrence of other color varieties of topaz from Katlang (light pink, colorless, or brown- Sample 2. Very pale tan; turned virtually colorless ish tones), in significantly greater quantities, the when heated to 500Â°Cthen turned dark orange- question arose as to whether these other topazes brown and pale tan in zones when subsequently would lend themselves to color alteration or im- irradiated (figure 16, middle row); subsequent provement by heat treatment and/or irradiation. heatings through 80Â°100Â° 120Â° 140Â° up to 250Â° Dr. Kurt Nassau was so kind as to carry out various caused slow decolorization to colorless. experiments in color alteration on pink, colorless, Conclusion: This material contains color cen-

150 Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 ters that cause intensification of hue upon irradia- PROSPECTS FOR THE FUTURE tion, but it subsequently bleaches when heated In recent months, the Gemstone Corporation of between 120Âand 250Â° for 15 hours; while not Pakistan (GEMCP)has extended exploration activ- tested, the irradiated material is almost certain to ities to other hills in the vicinity of Ghundao and bleach in daylight. has succeeded in locating occurrences of pink Sample 3. Colorless; upon irradiation turned dark topaz in the Shalzar Tangi and Rama areas, situated orange-brown, partly patchy, partly zoned; re- northeast of Ghundao and about 7 lzm south- verted to colorless when heated for 15 hours to southeast of Katlang. At present, detailed explora- 500Â°CFurther irradiation and reheating produced tion of these areas is in progress. There seem to be the same results, although one cleavage piece fair prospects for locating additional deposits. showed a slight trace of tan, but another showed a Pink topaz has never been and is still not an very faint blue (figure 16, bottom row). abundant gemstone. Hence, it is welcome news Conclusion: Same as for sample 2 above. that cuttable pink topaz of natural color is being found at various localities in Palzistan. The results of these experiments by Dr. K. Since GEMCP has also been successful in Nassau are similar to those he reported earlier for discovering new aquamarine deposits in other topazes (Nassau, 1974, 1975, 1980) exposed to parts of Kohistan, the gem world may expect gamma-ray irradiation and subsequent high-tem- Palzistan to produce more gemstones and addi- perature heating. Further experiments on the Kat- tional gemstone varieties, becoming an important lang topazes are planned. supplier to the gem market in the future.

REFERENCES Afridi A.z.K., Ali M.S., Malik RE. (1973)Economic aspects of 96-105. topaz of Ghundao Hill, Katlang, District Mardan. West Martin N.R., Siddiqui S.F.A., King B.H. (1962) A geological Palzistan Industrial Corp., unpublished report. reconnaisance of the region between Lower Swat and Indus Appleinan D.E., Evans H.T. (1973)Job 9214: Indexing and least- Rivers of Pakistan. Geological Bulletin of Punjab Univer- squares refinement of powder diffraction data. U.S. Depart- sity Vol. 2, pp. 1-14. ment of Commerce, National Technological Information Nassau K. (1974) The effects of gamma rays on the color of Service, Document No. PB-216 188. beryl, smoky quartz, amethyst and topaz. Lapidary Journal, Bambauer H.U., Taborszky F., Trochim H.D. (1971) WE. Vol. 28, No. 1, pp. 2040. Troeger's Optical Determination of Rock-Forming Min- Nassau K. (1975) Blue and brown topaz produced by gamma erals, 4th ed. Schweitzerbart'sche Verlagsbuchhandlung, irradiation. American Mineralogist, Vol. 60, No. 718, pp. Stuttgart. 705-709. BanlzH. (1976a)Rosafarbige durchsichtige Topase aus Palzistan. Nassau K. (1980) Irradiation-induced colors in gemstones. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Lapidary Journal, Vol. 34, No. 8, pp. 1688-1706. Vol. 25, No. 1, p. 41. Nassau K. (1984) Gemstone Enhancement. Butterworths, Bank H. (1976b) Farblose Topase mit hoher Lichtbrechung. London. Zeitschrift der Deutschen Gemmologischen Geseflschaft, Petrov I. (1977)Farbuntersuchungen an Topas. Neues Jahrbuch Vol. 25, No. 3, pp. 157-158. fur Mineralogie, Abhandlungen, Vol. 130, pp. 288-302. Chaudhry M.N., Howie R.A. (1970) Topaz from the Maldon Petrov I., Schmetzer K., Bank H. (1977a) Violette Topase aus aplite, Devonshire. Mineralogical Magazine, Vol. 37, pp. Palzistan. Necies Jahrbuch fur Mineralogie, Monatshefte, 7 17-720. Vol. 10, pp. 483-484. Chaudhry M.N., Shams F.A. (1983) Petrology of the Shewa Petrov I., Schmetzer I<., Bank H. (1977b) Violette Topase aus porphyries of the Peshawar plain alkaline igneous province, Palzistan. Zeitschrift der Deutschen Gemmologischen Ges- Northwest Himalayas, Palzistan. In F.A. Shams, Ed., Gmn- ellschaft, Vol. 26, pp. 152-156. ites of Himalayas, Karakoram and Hindu Kush, Punjab Petrov I., Schmetzer K., Bank H. (1977~)Chromhaltige violette University, Lahore, pp. 171-177. und orange-farbene Topase (ein Vergleich). Goldschmiede Giibelin E.J. (1982)Gemstones of Pakistan: Emerald, ruby, and Zeit~~ng,Vol. 4, pp. 43-44. spinel. Gems es> Gen~ology,Vol. 18, No. 3, pp. 123-139. Ribbe RH., Rosenberg RE. (19711 Optical and X-ray determina- Jan M.Q. (1979) Topaz occurrence in Mardan, Northwest tive methods for fluorine in topaz. American Mineralogist, Pakistan. Mineralogical Magazine, Vol. 43, pp. 175-176. Vol. 56, No. 9/10, pp. 1812-1821. Kempe D.R.C,(1983) Alkaline granites, syenites and associated Rosenberg P.E. (1967)Variations in the unit cell of the topaz and rocks of the Peshawar plain alkaline igneous province, their significance. American Mineralogist, Vol. 52, No. 11, Northwest Pakistan. In F.A. Shams, Ed., Granites of Hima- pp. 1890-1895. loyas, Karokoram and Hindu Kush, Punjab University, Spengler W.H. (1985)The Katlang pink topaz mine, North West Lahore, pp. 143-158. Frontier Province, Pakistan. Journal of Cemmolog~Vol. 19, Kornetova WA. (1950)~ber rosa Topase vom Fluss Kamenka. NO. 8, pp. 664-671. Akademiia Nauk (SSSR)Mineralogischski Muzei Tn~de,pp.

Pink Topaz from Pakistan GEMS & GEMOLOGY Fall 1986 151 CARBON DIOXIDE FLUID INCLUSIONS AS PROOF OF NATURAL-COLORED CORUNDUM By John I. Koivula

The question of how to identify natural- ntil the mid-1970s) when the practice of high-tem- colored from heat-treated corundum uperature treatment of corundum became widespread, has long puzzled the gemological liquid and gaseous carbon dioxide (COT.)fluid inclusions community. One important clue is now were commonly observed in Sri Lanlzan rubies and sap- provided by carbon dioxide fluid phires. In fact, the author has studied well over a hundred inclusions. Because such inclusions cannot survive heat treatment, their pieces of geuda (untreated) corundum with these inclu- existence intact and unruptured in sions. Traditionally, these inclusions have been useful in rubies and sapphires is conclusive proof establishing the natural origin of their host (Gubelin and that no heat treatment has occurred. Koivula, 1986). With the prevalence of heat treatment, however, they have taken on additional significance: Because carbon dioxide fluid inclusions cannot survive the temperatures required to alter color in corundum, their presence provides conclusive proof that the color also is natural.

HISTORICAL BACKGROUND Sir David Brewster, a Scottish physicist, first discovered C02fluid inclusions while examining sapphires and other single-crystal gem materials with the microscope. The year was 1823. Although he did not identify the liquid as carbon dioxide, he made note of his discovery and reported on this "remarkable new fluid found in the cavities of rocks" (Brewster, 1823).He observed that this strange new fluid was often found in the presence of water, although the two were immiscible (would not mix). The liquid had a refractive index less than that of water and a coefficient of thermal expansion approximately 30 times that shown by water. The fluid was also nonwetting and would ball up like elemental mercury rather than flow over and coat the interior walls of a negative crystal cavity. Since Brewster's discovery, the study of CO, fluid ABOUT THE AUTHOR inclusions has continued. With infrared absorption spec- Mr. Koivula is senior gemologist in the Research Department at the Gemological Institute of trometry (passing an infrared beam though a thin parallel- America, Santa Monica, California. windowed plate of a gem), inclusion investigators have The photomicrographs in figures 2, 3, and identified five separate forms of closely related carbon- 4 were taken by the author. oxygen compounds which may occur in fluid inclusions GI 1986 Gemological Institute of America (Roedder, 1972).Three of these are found in solution with

152 C02 Inclusions in Corundum GEMS & GEMOLOGY Fall 1986 Figure 1. The 1.84-ct Sri Lanlzan blue sapphire used in the experiment. Photo 0 Tino Hammid.

water: H2C03, HCO, - 1 and C03-2. The remain- rubies and sapphires have not undergone heat ing two, liquid and gaseous C02, are the ones of treatment. primary interest to gemologists concerned with Although Brewster was not referring to tem- the identification of heat-treated rubies and peratures anywhere near as high as those required sapphires. to effect a color change in corundum, it is nonethe- less surprising how little heat is required to actu- THE EXPLOSIVE NATURE OF C02 ally explode (shatter)a gem containing one or more As indicated by the following statement taken of these fluid inclusions. Brewster's statement from a letter written by Sir David Brewster to Sir regarding the application of heat "without danger" Walter Scott in 1835, Brewster had, through con- when the inclusion is "not near the surface" holds tinued experimentation, become aware of the ex- true for some gem corundums heated to tempera- plosive potential of C02 fluid inclusions when tures of only 250Â° to 400Â° (depending on the size heated: of the host gem, and the size, shape, and position of the COi fluid inclusion within the gem). It is not When the gem which contains the highly expansive true, as discovered experimentally by the author, fluid is strong, and the cavity not near the surface, for gems heated above 400Â°C Because of this heat may be applied to it without danger, but in the course of my experiments on this subject, the min- "explosive fatality," heat treaters of Sri Lanlzan eral has often burst with a tremendous explosion, rubies and sapphires commonly trim away areas of and in one case wounded me on the brow. the rough that contain inclusions, or partially saw, or even drill, into the inclusions. It is this explosive potential of C02 fluid inclu- If the C02inclusions are completely removed, sions (Koivula, 1980, 1980-198 1)that makes their then the gem has an excellent chance of surviving presence excellent positive proof that the host the 150VC-plus temperatures required to alter

CO, Inclusions in Corundum GEMS & GEMOLOGY Fall 1986 153 color in corundum. If they are not removed, the EMPIRICAL PROOF inclusion will explode and the gem will be badly To dramatically prove this point, the author se- damaged or completely destroyed. In either case, lected a 1.84-ct untreated blue Sri Lankan sapphire these inclusions will no longer exist. with a tiny, intact carbon dioxide fluid inclusion just beneath the table surface (figure 1). EXPERIMENTAL CONSIDERATIONS When the host sapphire was held below the Liquid carbon dioxide has a critical temperature of critical temperature of 3 1.2OC (88.2OF), both the 31.2OC (88.2OF).Above this temperature inclusions liquid and gaseous C02phases were visible within containing the liquid form of C02 homogenize the negative crystal (figure 2). Just a slight warm- into a uniform high-pressure fluid; as the tempera- ing above the critical temperature by the heat ture is increased above the critical point, pressure generated from the microscope lamp caused the also rises drastically. meniscus around the bubble to disappear (figure 3). When we consider that crystals containing C02 In the name of science, this gem was placed on a inclusions form under great pressure at consider- ceramic tile in an electric muffle furnace and the able depth within the earth, it becomes apparent temperature was gradually increased. A popping that if such crystals are now at the earth's surface, sound was heard when the temperature gauge on then the compensating pressure of the rock that the furnace indicated just 27PC. At this point, the once surrounded them is removed. Yet the inclu- furnace was turned off and allowed to cool. sions are still at their original high pressure of The stone was inspected. The C02fluid inclu- formation. So at room temperature we now have sion had exploded, blown a shard out of the table, corundum crystals containing fluid inclusions and left behind a crater (figure 4). with high outward pressure (1000psi or more) that have only external atmospheric pressure (instead CONCLUSION of tons of rock) to compensate. Many gem dealers today feel compelled to heat If we further aggravate this volatile situation by treat virtually every piece of corundum. Fine gems faceting, preforming, or trimming the stone and in no real need of treatment are subjected to the bring the inclusions closer to the surface (i.e., by furnace with the hope that a few extra dollars can cutting away layers of protective crystalline co- be cooked from them. Even gems that originally rundum that lend structural integrity to the crys- entered the market years before heat treatment tal)we have dramatically increased the chances for became popular are being burned for "improve- a pressure burst. It is easy to see, then, why stones ment." And little by little, inclusions that once containing C09 inclusions do not survive the gave natural, unadulterated gems uniqueness are application of heat energy. disappearing. The heat treater's furnace is acting as

Figure 2. Negative crystal filled with liquid Figure 3. The same Cop-fillednegative crystal and gaseous carbon dioxide as observed as in figure 2 but just above the critical below the critical temperature. Dark-field temperature (31.2OC) for carbon dioxide. Dark- illumination,w magnified 50 x . field illumination, magnified 50 x .

154 COi Inclusions in Corundum GEMS & GEMOLOGY Fall7'"' Crowningshield, pers. comm.). Mr. Crowning- shield's observation concerning the Gem Trade Laboratory is an important one. The more prevalent heat treatment has become, the fewer of these inclusions are seen. Carbon dioxide fluid inclusions will not survive heat treatment. Therefore, an unruptured carbon dioxide fluid inclusion in a ruby or sapphire is absolute proof that the gem is natural and has not been heat treated.

REFERENCES Figure 4. The same negative crystal as shown Brewster D. (18231 On the existence of two new fluids in the in figures 2 and 3 hut after exploding. The cavities of minerals, which are immiscible and which gem was heated to only 270Â°C Dark-field and possess remarkable physical properties. Edinburgh Philo- shadowed oblique illumination, magnified 50 x . sophical Journal, Vol. 9, pp. 94-107. Giibelin E.J., Koivula J.I. 11986) Photoatlas of Inclusions in Gemstones, ABC Edition, Zurich. a gem-blender, slowly homogenizing the corun- Koivula J. I. (1980) Fluid inclusions: hidden trouble for the jeweler and lapidary. Gems &> Gemology,Vol. 16, No. 8, pp. dum population and making the relatively com- 273-276. mon appear rare to the uneducated. Koivula J.I. (1980-1981) Carbon dioxide as a fluid inclusion. As a consequence, very few COi fluid inclu- Gems d Gemology, Vol. 16, No. 12, pp. 386-390, Roedder E. (1972)Data'of geochemistry, chapter JJ, composition sions in corundum have been seen in the GIA Gem of fluid inclusions. Geological Survey Professional Paper Trade ~aborator~during the last few years (R. 440-JJ. . I

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COi Inclusions in Corundum GEMS & GEMOLOGY Fall 1986 155 CONTRIBUTIONS TO A HISTORY OF GEMOLOGY: SPECIFIC GRAVITY - ORIGINS AND DEVELOPMENT OF THE HYDROSTATIC METHOD By John Sinkankas

Thedevelopment of the hydrostaticmethod he first useful method of comparing the densities of of specific gravity determination as applied T substances as an aid to identification is attributed by to gems is traced from Archimedes's Vitruvius (ca. 13 B.C.) to Archimedes, the famous Greek discovery to the present, with brief scientist (ca. 287-212 B.C.). As the story goes, historical remarks supplied on other Archimedes was asked by King Hieron I1 of Syracuse to methods. This is the first in a series of determine if a newly delivered crown was pure gold as articles on the history of gemology that will claimed by its maker. Archimedes received the inspiration appear periodically in Gems & Gemology. for his now-famous displacement method of determining comparative densities when he stepped into a brimming bathtub and noted the overflow caused by the added volume of his body. Inspiration struck-Eureka! -the water displaced must be equal to the volume of any material inserted into it, and hence it must follow that for substances of equal weight, a "lighter" or less dense substance would displace more water than a "heavier" or denser material. A comparative volumetric displacement test of the crown and a mass of pure gold equal to it in weight showed that the crown displaced more water, hence it had to be "lighter," hence it had to be adulterated. This fundamental principle first enunciated by Archimedes is basi- cally the one that we still follow in all measurements of specific gravity involving immersions in fluid. Inciden- tally; the scoundrelly goldsmith was executed. Although little progress was made in the hydrostatic measurement of specific gravity during more than 10 centuries following Archimedes's discovery, the increased interest in gemstones from the late 17th century on led to fairly rapid developments both of the method and of specific values from that time. Today, the hydrostatic technique for measuring specific gravity is a standard test in ABOUT THE AUTHOR gemstone identification (see box). The following discus- Dr. Sinkankas is the author of numerous books and sion traces the origins and development of this very basic articles on lapidary work, mineralogy, occurrences gemological tool. of gemstones, andprospecting and collecting. With his wife, Marjorie, he operates Peri Lithon Books, in EARLY DENSITY TESTS San Diego, CA, a mail-order antiquarian book business devoted to the earth sciences and related OF PRECIOUS METALS fields. Differences in weight among objects of equal size were 07986 Gemological Institute of America appreciated in Roman times according to Ball (1950),who

156 Specific Gravity GEMS & GEMOLOGY Fall 1986 THE HYDROSTATIC METHOD OF DETERMINING SPECIFIC GRAVITY The Archimedes principle states that an object immersed in water displaces a volume of water equal to its own. Thus, when Archimedes stepped into his bath, the water level rose. In addition, however, the water (or any liquid, for that matter) exerts a buoyant force upwards on the immersed object, against the downward force of gravity, and the object appears to have lost weight in comparison with its weight in air. This loss of weight is the same as the weight of an equal volume of water (theamount displaced, in fact). The hydrostatic method of determining specific gravity depends on these simple laws of physics. First, one weighs the gemstone in the normal manner on an accurate balance. Since specific gravity is a ratio, any unit of measure (carats, grams, etc.) will do. The balance is then set up with a special apparatus such as that shown in figure 1. The stone is placed in the wire basket suspended in the container of water ~ and its new weight can then be measured. I The numeric value for specificgravityis the ratio 1 of an object's weight in air to that of an equal volume ,I of water, which can be found by the formula: I ,*.. wt. in air ! , i , (wt. in air) - (wt. in water) Figure 1. A contemporary balance used for the The term density is often used interchangeably hydrostatic determination of specific gravity, with specific gravity but, while the numeric values , derived for each are nearly the same, the former is i actually the mass per unit volume of a substance and The use of precious metals as marks of wealth is expressed in grams per cubic centimeter (g/cm3). Specific gravity-a ratio-has no unit. and, more importantly, as media of exchange in commerce, early established a need for standardiz- I ing the proportions of gold and silver (theprincipal alloying metal) in coins and in other applications. summarized the gemological content of Pliny's According to Smith and Forbes (19571, crude Natural History of 79 A.D. Ball noted early lznowl- means of specific-gravity determination were edge concerning the heaviness of placer gold and developed as early as the sixth century when "a that the ancient miners took advantage of this balance with a graduated beam and movable ful- property to separate the gold from lighter rock crum was described in the poem Carmen de Pon- particles. Pliny himself was aware of differences in deribus (Poem on Weighing) attributed to Pris- weight among lighter objects, such as precious cian.'' They further note that as early as the 1 lth stones, for as Ball states, "Pliny's first test for dif- and 12th centuries a list of weights of metals rela- ferentiating genuine precious stones from glass tive to wax was compiled for the purpose of assist- imitations is weight, for ordinarily the genuine ing a foundryman to determine how much metal stone is heavier than the false." Egyptian records to melt. "By the seventeenth century extensive indicate that even before Pliny's time the heavi- tables of similar [specific gravity] data became ness of gold was well known and used in concen- common in mathematicians' works." A table de- tration operations during gold mining (Forbes, vised particularly to help the assayer appeared in 1950). Davies (1809) refers to the work De lJon- the 13th century, and by the close of the 16th deribus et Mensuribus (Weighing and Mensura- century, not only were the principles understood tion), written approximately 45 A.D. by Quintus but man's ingenuity was also being turned Remnius Palaemon, which showed how specific to the design and manufacture of more precise gravities of solids could be ascertained. balances.

Specific Gravity GEMS & GEMOLOGY Fall 1986 157 SEVENTEENTH- AND EIGHTEENTH- CENTURY EUROPE: DENSITY TESTING OF GEMSTONES BEGINS A notable experimentalist was Francis Bacon (1561- 1626)) who drew up a table of densities, published some time after his death, which Davies (1809, p. 537) believed to be "the oldest table of specific gravities now extant." Davies also cited an even earlier contribution, that of Marinus Ghetal- dus (1566- 1626), who made his own hydrostatic experiments "with care and exactness," and in 1603 published a treatise on weighing. Ghetaldus is credited with determining the first specific gravity for any metal (Debus, 1968).Other early exper- imentalists include Johannes Baptista Villalpan- dus (1552- 1608) and Marin Mersenne (1588- 1648). Possibly because the evaluation of specific gravity of gemstones was of little concern in the early 1600s, we find that Boetius de Boodt (1550- 1634))who may justifiably be called the "Pliny of Gemology," says nothing more about differing gemstone densities than that they exist (1647).He gives no hint that any method of placing a numeri- cal value on this property existed among gem dealers and jewelers of the time. It is, of course, possible that because gems are usually very small relative to other materials, existing apparatus could not be counted on to afford consistent, reliable results. In contrast, chemists and physicists of the same period were actively measuring densi- Figure 2. Plate V from the second volume of ties, devising better methods and instrumenta- Robert Boyle's collected works (P. Shaw edition tion, and defining the limitations of the hydrosta- of 1725) showing his specific-gravity balance and tic method. For example, Robert Boyle (1627- associated accessories. Theprincipal parts are 1691)) best known among gemologists for his the stand C-Cand the rather elaborate means for Essay about the Origins and Virtues of Gems raising and lowering the beam A-Aand pans B-B (1672). produced a treatise in 1666 titled Hy- with pulleys and weight (thesmall lion on the drostatical Paradoxes Proved and Illustrated by right, erroneously marked L). The specimen L (on Experiments (Boyle, ed. by Shaw, 1725). the lower left) is shown suspended by horsehair Boyle tested a variety of substances, including Kin the water bucket M-M. Grain weights are in gem materials, with the balance shown in figure 2, container 0,larger weights (nested)are in Q, jar N holds the water supply, and the forceps Pare but preceded his remarks with advice on how to go used to handle weights. about obtaining the greatest accuracy. First, he describes the balance and its parts and accessories. He then states that he found horse hair to be the equally as informative, for example, avoiding best suspension thread because "its weight usually bubbles, and the like, such that one cannot help differs so little from that of water, that the differ- but admire his thoroughness. ence may be safely neglected." However, he ad- Boyle stressed the value of S.G. determina- vises that an equal quantity of hair,, as was used to tions in the detection of frauds and substitutes fasten the specimen for immersion weighing, be because they "may assist us to guess, with proba- placed in the opposite pan to reduce error. Other bility, whether a mineral body be of a stoney na- instructions for specific-gravity weighings are ture, or not." He was referring specifically to

158 Specific Gravity GEMS & GEMOLOGY Fall 1986 speculations at the time as to the exact nature of coral, which some thought to be apetrification and The Hydro/tatfeal Balance. others some sort of plant. Boyle tested a fine IVeigh'd In Wi- Prapcrtion. specimen of red coral and obtained an S.G. of 2.68; Another - - -- Another from famica. - - - he noted that this value "exceeded that of crystal Lead-ore - - -- Another piece from Cumberland, rich [quartzIl1'and concluded that "their opinion, who Manganefe, a piece - - take it for a stone, seems most probable." The Marcafite - - Another from Antfridge - - animal nature of coral was not established until Another more Jhining than ordinary Mineral, Corn@, like a (hining mar- about 1723 (by J. A. Peyssonel, 1694-1759; see cdtie - -- - Ore of Glver, choice from Saxony - Lacaze-Duthiers, 1864).In connection with coral, Another piece - - - - and to emphasize the usefulness of S.G. determi- OReocolla - - - - Rhinoceros's horn- - - nations, Boyle manufactured some realistic coral Rock-c - - - slat, IrzRa1- - imitations and then showed how these were easily 8dph11rvivum - - - German, very fine - - detected on the basis of S.G. "notwithstanding Talc, a piece like Lapi1 Amiaatlmi their fine colour, shape, and gloss." Other tests fietian - - - were made on preparations of "pastes or factitious of Jamaica - - - - Tm-glafs - - - - gems," made with red lead (minium),which again Tin-ore, New-Englifi - - - Tin-ore, black, rich- - - were easily distinguished on the basis of their spe- Another piece, choice - - Tutty, a fin Ie piece -- - - cific gravities. Vitriol, ~nxfa ilery fine piece- With regard to pearls, which he also tested, fitrum Atttimmii -- - Boyle makes the significant remark that specific- Unicorn's horn, a piecw- * Later trials have furnith'd us with ties of folids and fluid#. gravity weighings are nondestructive in nature, the following tablo of the fpccific grxvi- 1 . and "a pearl, for instance, is discoverable to be A T^BL E of the /pacific Gravities if feveral JXd counterfeit;without the least prejudice to it." On and JuId 'Bodies. one "monstrous" (206 grains) baroque pearl, he determined a specific gravity of 2.51. Because of his interest in disclosing the frauds then prevalent in medicine, Boyle included in his tests the enor- mously expensive bezoars and other calculi to show that these organic materials, whatever their medicinal values, could be readily distinguished The Hydroflatjcal Balance. from mineral concretions of like appearance. At A diamond---3,400 %rum ofhumam bld-t,t90 Clcar crynal gIafi---3,150 Pitch -----I,I,., the end of his discourse, Boyle provided the results Ifland oryI3al ---2,iao Spirit of fall ----1.130 Fine marble -----Ãˆ,7o Spirit of urine -----t,tz* of his tests in the form of tables which are repro- Rock-cryflnl-----1,690 Human Mood---r,qo Common green filtfi ----2,6zo Amber -----I,~~ stone "fa man gravity --a,$m Milk ------( O.*o duced here as figure 3; note that some gemstones S^l .qimm, ----%,I@; Urine -----1.~3.~ . Brick --Ãˆ,c Dry b~x-wd-----~~~~ are included. Filrc, -----1,900 sn-watcr ----1,03~ Alabaflcr ----1,875 Corninon water ----I ,000 Also during the first half of the 18th century, Dry ivq- --I$%$ Camphim --- Bnmhc-----r,800 BCCI-wax------0,95~ ~~996 D.mtv,k John Ellicott (?1706- 17721, noted instrument vitriol ----I,~Is Linfd oil ----0 995s Alun, ----1,714 Dr oak -0.915 maker and scientist, very precisely determined the Bocax-----1,~14 0i/oliv~=-~-=- 89'5 c#ld#,btt-u -- -1 ,loo Spr oi turpn~ine- -0.61~ specific gravity of a series of 14 large diamonds, 011 of vitriol---1,im e81ficdrplru of winc--,866 Oil of iattar----1,550 Dry ah----0,800 four from Brazil and 10 from the "East Indies" Bcioar- 1,500 Dry mapic -Ã‘Ã‘Ã‘Ã‘Ã‘Ã‘Ã‘ Honey - ~$0Dry elm ---dm Gum mhic ---1,~15 Dry fir - --- 0.5~" (Borneo?).The stones included some that were in S iritofnitrc --1,315 C?k-----do a 8 40 excess of 29 ct [Davies, 1809).It was the size of the A"afir,*-- -1,300 I*,x -----,.=.,I stones that inspired Ellicott to undertake the determinations, because hitherto most test specimens had been only a few carats or less. Ellicott's values, 3.501-3.525, average 3.517, compare fa-

Figure 3. Robert Boyle's tables of specific-gravity values obtained through the use of the apparatus shown in figure 2 (from the P. Shaw edition of 1725).

Specific Gravity GEMS & GEMOLOGY Fall 1986 159 to specific gravities according to season, summer to winter, which serve as a crude set of tempera- PESANTEUR ture corrections. In 1798, Charles Francis Greville ( 1749- 1809) published an extensive description of the corundum~of Asia, which also appeared in abridged CORPS. form (Davies, 1809,Vol. 18, pp. 356-378).He provided S.G. tables for a number of varieties of co- Onvragc utilc Si I'Hiftoire NaturcIIe , 5 la rundum, as reported by earlier researchers, as well Pliyfique, aux Arts & au Commerce. as values for topaz and diamond. Among the most important specific gravities incorporated in Davies's tables are those of P. van Musschenbroek ( 1692- 1761), the celebrated Dutch scientist, which were first published in his Elementa Physicae (1734) and republished, en- larged, in his Essai de Physique (1739). These values were consulted by M. J. Brisson (1723- 1806)) the famous French physicist, during his compilation of Pesanteur Spkcifique des Corps (Specific Gravities of Bodies). Published in 1787, this is clearly the most accurate and complete of all specific-gravity compilations of that period (figure 4). A German translation by J. G. L. Blum- A PARIS, hof, with some rearrangement and augmentation, DÂ L'IMPRIMERIE ROYALE. was published in Leipzig in 1795. Both works are 4 rare, which may account for their neglect by most M. UCCLXXXVII. gemological historians; only B. W. Anderson (1938) notes Brisson's original treatise and pro- i vides a thoroughly detailed and admirable analy- Figure 4. Title page of Brisson's 1787 work on sis. Brisson explains his methods, his apparatus, specific gravity. his standard use of rainwater as an immersion fluid, and the adoption of a standard temperature for measurements. As a result of his care, his vorably with today's generally accepted range of values are in most instances remarkably close to 3.514-3.518 (Bruton, 1978). those considered acceptable today. Brisson recog- Great interest was aroused throughout Europe nized that specific-gravity values tend to be con- by the density information that the hydrostatic stant for minerals and urged that these values be method could provide for many substances, as used in conjunction with obvious external fea- shown in the lengthy article and extensive tables tures-especially crystal forms (of which he proof Richard Davies, M.D. (d. 1768), originally pub- vided two engraved plates), and also color, hard- lished in the Philosophical Transactions of the ness, and the phenomenon of double refraction- Royal Society of London (Vol. 45, No. 488, 1748, to identify gemstones in particular, thus setting pp. 416-489) and republished in abridged form forth the first scientific proposal for gemstone (Davies, 1809). Davies provided an excellent his- identification. His scheme precedes even that used torical summary, including a survey of investiga- by Haiiy in his epochal gemological treatise (1817), tors and their methods and findings, beginning which will be described below. Brisson was re- with Archimedes. He then incorporated the find- markably thorough in obtaining specimens to test, ings of Ghetaldus, Villalpandus, Mersenne, Boyle including gemstones; scarcely any known at the and others into 11 tables, each with numerous time failed to catch his attention. By exercising his entries and citing sources for same; three of these prestige and position, he obtained the loan of the tables (1,3, and 4) contain data on gem materials. Regent diamond from the French Crown Treasury The 11th table provides adjustments to be applied and was the first to establish its specific gravity.

160 Specific Gravity GEMS & GEMOLOGY Fall 1986 By the end of the 18th century, the usefulness real turquoise and "bone turquoise." Color as a of the hydrostatic method was everywhere ac- first argument remains very much in use today, for knowledged and specific-gravity values had be- example, in B. W. Anderson's Gem Testing (1980). come routine data in numerous chemical and Within each table, Hauy gives columns for light physical treatises. Among gemological textbooks, phenomena, specific gravity, hardness, single or for example, which also incorporated such data, double refraction, electrification by friction, same that of C. Prosper Brard (1788-1838), Trait6 des by heat, and magnetism (undoubtedly his inclu- Pierres Prdcieuses (18081, provided a list of sion of electrical/magnetic properties was in- gemstone specific gravities, in descending order, spired by his investigations of these phenomena at from zircon to amber, and a list of weights per about the time that he became interested in gem- cubic foot of various ornamental and building stones). The importance of Hauy's treatise was stones. Shortly afterward, in 1813, J. B. Pujoulx immediately recognized and led to a German edi- (1762-1821) published an economic mineralogy tion (1818) and an Italian edition (1819). In 1825, which stressed the importance of correlating prop- Hauy issued a pamphlet summary of the main erty values and features in gem identification, and work with a series of crystal drawings. described the structure and use of the Nicholson In 1832, two important gemological texts ap- hydrometer for taking specific gravities. peared with significant information on specific gravity: the first, a small "pocketbook" by J. R. THE NINETEENTH CENTURY: Blum (1802- 1883); the second, a much more de- SPECIFIC GRAVITY ASSUMES A KEY tailed work by P. Bouk. Blum provided an exten- ROLE IN GEM IDENTIFICATION sive table of color versus specific gravity that in In 18 17, a large and detailed discussion of specific part followed Hauy's scheme. Bouk's work devoted gravity and its importance in mineralogical iden- more space to specific gravity and incorporated an tification'appeared in the Propadeutik der Min- engraved plate that depicted a balance with a slid- eralogie of! C. C. Leonhard, J. H. Kopp, and C. L. ing weight on the arm (figure5), which design Bouk Gaertner, which also provided a history of previ- claimed was invented by Brard, although the latter ous investigations as well as a large table of said nothing about it in his 1808 book. An impor- specific-gravity values ranging from several sub- tant novelty of Bouk's treatise is his inspection stances less dense than water to gold. Another table for specific gravity (Vol. 2, plate 3). important table provided temperature corrections The first book after Brisson (1787) to devote for weighings in water. This year also marked the itself solely to the specific gravity of mineral sub- appearance of R. J. Hauy's landmark work, Trait6 stances was M. Websky's 1868 work, which cou- des Caract6res Physiques des Pierres Prdcieuses pled specific gravities with increasing hardness in (Treatise on the Physical Characteristics of Pre- a series of ranges from S.G. 0.4-0.7 to S.G. 12-25. cious Stones). While gemstone species are included, they are not While the fundamental concept of correlating specifically designated nor are they treated sepa- several properties or features to achieve identifi- rately. Subsequent gemological treatises have in- cation had already been clearly enunciated by Bris- cluded S.G. data. The most extensive S.G. table for son, with whose work Hauy was familiar, it was minerals and gemstones currently available is in left to the latter to write the first usable textbook, the Gemstone and Mineral Data Book (Sinkan- per se, of gem identification in which the reader is lzas, 1972). told what all the properties are, why they are characteristic, and how they may be measured, tested, OTHER METHODS OF or observed. This general discussion is followed by DETERMINING SPECIFIC GRAVITY 11 tables that are surely the first of their kind as Although no attempt has been made in this contri- applied to gemstones and the model for many bution to discuss other methods of determining others published since. The first argument is color, specific gravity, a few notes on them may be of hence the tables are headed colorless, red, blue, interest to place the hydrostatic method in per- green, etc., with a "red-brown" table for zircons, spective. The pycnometer, or specific-gravity bot- another for gems displaying reflecting phenomena tle, is sometimes used in gemological determina- such as asterism and adularescence, and a final tions. This special glass flask is first filled with table for opaque gems of blue-green color, that is, water, then weighed; next the flask is emptied and

Specific Gravity GEMS & GEMOLOGY Fall 1986 161 Figure 5. Plate3 from Bond's treatise on jewelry showing a sliding weight beam balance ("Fig. 1") with pans for weighing in air and weighing in water. When the specimen K is placed in the upper pan, one of the weights marked Cisselected to balance the beam, and the slider Ais adjusted togive the final balance. When the specimen is placed in the lower pan C, the difference between the slider positions gives loss of weight in water. the gem fragment or cut gem inserted; last, the its ease of operation than to any increase in accu- bottle is refilled with water and weighed again. racy. It also suffered from severe capacity re- The displacement of water by the gem material strictions which required, in the case of cut-gem measures gem volume and hence enables the spe- weighings, that a series of instruments be manu- cific gravity to be determined. There are various factured to accommodate different sample forms of pycnometer bottles, a common type being weights. A typical Nicholson hydrometer is that shown in figure 6. According to Darmstaedter shown in figure 7. The crucial place on the instru- (1908),the first pycnometer can be traced to 1121 ment is the slender neck between the upper pan A.D. and a certain Arabian savant, named Alkha- and the large hollow body, because it is along this zini, who investigated the specific gravity of fluids. neck, suitably graduated, that the difference is The modern form of the pycnometer was devised noted between a weighing with the gem in the in 1699 by chemist Wilhelm Homberg upper pan (weight in air) and in the lower pan (1652-1715). (weight in water). Ordinary glass hydrometers can The simple yet effective hydrometer invented be modified to become crude Nicholson instru- by the ingenious English instrument maker, Wil- ments, if one chooses to experiment with this liam Nicholson (1753- 18 15)) around 1787 was device. greeted everywhere with enthusiasm due more to Another S.G. instrument, again inspired more

Specific Gravity GEMS & GEMOLOGY Fall 1986 by the need for quick determinations than for ac- summary of the problem, investigators, instru- curacy, is the Jolly balance shown in figure 8. It is mentation, etc., appears in Thorpe (1913).Thorpe named after its inventor, P. J. G. von Jolly claims that the first use of heavy liquids for S.G. (1809-1884), and depends for its operation on the determination can be dated to 1862, but the first extensibility of a tapered spring of many turns liquid generally adopted for the purpose is from which hangs a double-pan arrangement; the upper pan is for in-air weighings and the lower one, immersed in water, for in-water weighings. Differ- Figure 7. Nicholson's hydrometer. Upper pan F-K ences in weight are indicated by a pointer attached is for "in-air" weighing, readings are taken from to the spring which moves against the vertical graduated stem b, 0-S is the boyancy float, and scale on the same column that supports the spring. E-G, the lower pan, is for "in-water" weighing. Even today, the Jolly balance is used much more Not shown: glass cylinder in which apparatus floats in water. From Kobe11 (1864, p. 115). frequently than either the beam balance or the Nicholson hydrometer; the latter is actually now an antique of considerable collection value. The influence of liquids of densities higher (or lower) than water on the flotation of solids must surely have been apparent to man at some very distant age in the past, but only in relatively recent times was it deemed feasible to use heavy liquids as indicators of the specific gravity of the solids immersed in them. While a simple "sink or float" test was indicative, it was also found that certain liquids could be diluted to provide an entire range of knownidensities, so that a precise determination on a given sample became possible. A good

Figure 6. A pycnometer, or stoppered glass bottle, for determining specific gravity. From Groth (1887).

Specific Gravity GEMS & GEMOLOGY Fall 1986 163 those mentioned above have been developed and are still used in relative safety for the immersion method of gem testing. For a valuable review of the problems associated with suspension separation of minerals in heavy liquids, including a large number of abstracts of pertinent literature, see P. G. H. Boswell (1933) and also the large paper by J. D. Sullivan (1927).A fascinating account of weighing and the use of scales and weights throughout the ages is contained in B. Kisch (1965). Lastly, it should be mentioned that various instruments have been devised to measure the volume of water displaced by a solid. A very obvious and simple method is to place a specimen in a graduated cylinder filled to a certain mark with water, and then to note the apparent increase in water volume which, of course, gives the volume of the immersed object.

CONCLUSION The hydrostatic method of S.G. determination, now more than 2,000 years old, is still an excellent method for obtaining rapid results without the need for possibly dangerous test substances. How- ever, its accuracy drops sharply when small specimens or cut gems are used, and for the latter immersion fluids may prove to be faster and more convenient. For extremely accurate determinations, many investigators still employ some form of pycnometer under carefully controlled conditions in conjunction with a very precise analyti- cal balance. Figure 8. Jolly balance, still much used for rough determinations ofspecificgravity of largegems or mineral specimens. Courtesy of Eberbach Corporation, Ann Arbor, MI. REFERENCES Anderson B.W. (1938) Brisson's "Pesanteur Spkcifique des Corps." Gemmologist, Vol. 8, No. 87, pp. 36-38. Sonstadt's or Thoulet's solution, first proposed by Anderson B.W. (1980) Gem Testing, 9th ed. Butterworths, Sonstadt in 1874. The usefulness and convenience London. Ball S.H. (1950)ARoman Book of Precious Stones. Gemologi- of a number of heavy liquids is counterbalanced by cal Institute of America. Los Angeles.-. CA. their noxious or even actively poisonous proper- Bauer M. (1896)~delsteinkunde. Leipzig. ties. However, the discovery of methylene iodide, Blum J.R. (1832) Taschenbuch der Edelsteinkunde. Stuttgart. Boodt A.B. (1647) Gemmarum et Lapidum Historia, 3rd ed. a relatively safe compound, and its use in petro- Leyden. graphy (Brauns, 1886) led also to its adoption for Boswell P.G.H. (1933) On the Mineralogy of Sedimentary testing gems. The first gemological textbook to Rocks. Thomas Murby, London. Bou6 P. (1832)Trait& dJOrfevrerie, Bijouterie et Joaillerie. Vols. incorporate instructions on the use of heavy 1 and 2, Paris. liquids was that of P. Groth (1887).Much more Boyle R. (1725)The Philosophical Works of the Honourable elaborate instructions then appeared in Max Robert Boyle, Esq., Vol. 2. Abridged by Peter Shaw, London. Bauer's classic text, Edelsteinkunde (1st edit., Brard C.P. (1808) Trait6 des Piems Pr6cieuses. Vols. 1 and 2, 1896).In the course of time, other liquids besides Paris.

164 Specific Gravity GEMS & GEMOLOGY Fall 1986 Brauns R. (1886)Ueber die Verwendbarkeit des Methylenjodids Kobe11 F. von (1864) Geschichte dar Mineralogie. J.G. Cot- bei petrographischen und optischen Untersuchungen. taschen Buchhandlung, Stuttgart. Neues Jat~rbuchfur Mineralogie, Vol. 2, pp. 72-78. Lacaze-Duthiers H. (1864) Histoire Naturelle du Corail. J.B. Brisson M.J. (1787) Pesanteur Sp6cifique des Corps. Paris. Ballikre, Paris. Brisson M.J. (17951 Die spezifischen Gewichte der KOrper. Leonhard C.C., Kopp J.H., Gaertner C.L. (1817jPropadeutik der Trans. by I.C.L. Blumhof, Leipzig. Mineralogie. Frankfurt Am Main. Bruton E. (19781Diamonds, 2nd ed. Chilton Book Co., Radnor Musschenbroek P. van (1739)Essai de Physi(l~~e,Vols. 1 and 2. PA. Trans. by P. Massuet, Leyden. Darmstaedter L. (1908)Handbuch zur Geschichte der Natiir- Nicholson W. (1787) Description of a new instrument for wissenschoften und der Technil<.Julius Springer, Berlin. measuring the specific gravity of bodies. Memoirs of the Davies R. (1809) Tables of specific gravities, extracted from Manchester Literary and Philosophical Society, Vol. 2. various authors, with some observations on the same. In Pujoulx J.B. (1813) Minkralogie a 1'Usage des Gens dii Monde. The Philosophical Transactions of the Royal Society of Paris. London, Abridged, Vol. 9, pp. 536-553. Sinkankas J. (1972)Gemstone and Mineral Data Book. Win- Debus A.G. ed. (19681 World Who's Who in Science. A.N. chester Press, New York. Marquis Co., Chicago. Smith C.S., Forbes RJ. (1957) Metallurgy and assaying. In C. Forbes R.J. (1950) Metallurgy in Antiquity. E.J. Brill, Leiden, Singer et al., eds., A History of Technology, Vol. 3, Oxford The Netherlands. University Press, New York and London. Groth P. (18871 Grundriss der Edelsteinkunde. Leipzig. Sonstadt E. (1874) Note on a new method of taking specific Hatiy R.J. (1817) Trait&des CaractAres Physiques des Pierres gravities, adapted for special cases. Chemical News and Prdcieuses. Paris. Journal of Physical (Industrial) Science, Vol. 29, Hatiy R.J. (18181 Ueber den Gebrauch physikalischer Kenn- pp. 127-128, zeichen zur Bestimmung geschnittener Edelsteine. Trans. Sullivan J.D. (1927) Heavy liquids for mineralogical analyses. by K.S. Leonhard, Leipzig. U.S. Bureau of Mines, Technical Paper 381. Hatiy R.J. (18191 Trattato dei Caratteri Fisici della Pietre Pre- Thorpe E. (19131 A Dictionary of Applied Chemistry, Vols. ziose. Trans. by L. Configliachi, Milan. 1-5. London. Hatiy RJ. (1825) Distribution Technique des Pieties Prd- Vitruvius P.M. (ca. 13 B.C.] De Architecture. cieuses, avec Leurs Caract&res Distinctifs. Vienna, Websky M. (1868) Die Mineral-Species nach den fur das Kisch B. (1965)Scales and Weights: A Historical Outline. Yale specifjsche Gewicht derselben . . , Werthen. Breslau. University Press, New ~aven,CT. . ,

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Specific Gravity GEMS & GEMOLOGY Fall 1986 165 NOTES AND NEW TECHNIQUES

COLOMBAGE-ARA SCHEELITE By Mahinda Gunawardene

A new deposit of scheeli te wiis discovered in 1983 near 1976, and Arem, 19771, although it is a very attrac- Ratnapura, Sri Lanka. This article analyzes the gemo- tive collector's stone (figure 1).The physical prop- logical properties of this rare gem mineral, and com- erties of scheelite, such as refractive index and pares them with those recorded for scheelites from specific gravity, are comparatively high, but the Mexico and the United States. mineral is soft (4.5-5 on the Mohs scale).Cuttable gem material has been found in the United States in California, Arizona, Utah, and Nevada, as well as in Mexico, Czechoslovakia, Italy, Switzerland, In 1983, a new occurrence of gem scheelite was Finland, France, England, Korea, and Australia. discovered near the village of Colombage-Ara, not far from the city of Ratnapura, Sri Lanka. The LOCATION AND OCCURRENCE author obtained a parcel of faceted stones from a The village of Colombage-Ara lies on the south- Ratnapura dealer who had represented them as western edge of the Udawalawe reservoir, approx- rock crystal quartz. imately 5 km northeast of the main road between The scheelites examined by the author were Ratnapura and Embilipitiya, in southern Sri reportedly found in a small pegmatite vein near Lanka. Colombage-Ara, approximately 80 km south- Scheelite in rocks of Precambrian age has been southeast of the city of Ratnapura. Preliminary reported in Colorado and Wyoming by Tweto examination with a 10 x lens and a diffraction gra t- (1960) and Argall (19431, and is disseminated in ing hand spectroscope helped to identify the regionally metamorphosed rocks, mainly in cal- stones. Since the refractometer failed to provide a shadow-edge on the scale, the stones were first thought to be zircon, especially as a lox lens exhibited double images of the rear facet edges. How- ever, the spectroscope revealed a rare-earth spec- ABOUT THE AUTHOR trum, with lines centered around 584 nm, instead Mr. Gunawardene is president of the Lanka Foundation for of the absorptions typical for zircon. This con- Gemstone Research in Colombo, Sri Lanka, and director of MANYGEMS, a wholesale gem import firm in Heltenrodt, West firmed the colorless samples to be the first gem Germany. scheelites discovered in Sri Lanka. Acknowledgments: The author gratefully acknowledges Dr. Scheelite is colorless in its purest state, but the Henry A. Hgnni of Basel University, Switzerland, for performing allochromatic gem can occur in a wide variety of the chemical analysis: and G. Bosshart, of the Swiss Foundation colors, including orange, yellow, green, purple, for Gemstone Research in ZOrich, Switzerland, for providing the visible-light absorption spectrum diagram. Sample scheelites brown, red, and many shades of gray. Few refer- from other localities were graciously provided by Walter Lorenz ences to this CaW04 mineral are found in the of ldar-Oberstein, West Germany. gemological literature (see, for example, Webster, 0 7986 Gemological Institute of America

166 Notes and New Techniques GEMS & GEMOLOGY Fall 1986 Visual Appearance. Most of the scheelites from Colombage-Ara are colorless. However, a yellowish hue is visible in a few samples, and grayish white stones have (though rarely) been seen. The gem scheelites are clean with good transparency. A few, especially those that are grayish white, are semi-transparent to translucent.

Refractive Index. Shadow-edge observations on a Riplus refractometer indicated that the ranges of refractive indices for Sri Lankan scheelites are 1.920- 1.922 and 1.930- 1.935. The approximate birefringences calculated range from 0.012 to 0.015. Figure 1. These three scheelites were among the first 55 gem scheelites found in Colombage-Ara, i Sri Lanka. Thelarge onein the upperportion of the Specific Gravity. Specific gravity was determined photo weighs 12.20 ct and the other two,6.35 and on a Mettler electronic carat scale with a hydro- 7.42 ct, respectively. static attachment. The Colombage-Ara scheelites were found to have specific gravities between 5.94 and 6.30; the upper limit is considerably higher cosilicate gneiss. Similar geologic conditions exist than the upper limits for scheelites from other in Sri Lanka in Precambrian rocks of the Highland localities (Webster, 1976). series (Munasinghe and Dissanayake, 1981). The district surrounding the towns of Colombage-Ara Reaction to Ultraviolet Radiation. All of the Sri and ~atnaiurais located in the southern part of the Lankan scheelites tested fluoresced a clear whitish metamorphic rock assemblage. or chalky blue when exposed to short-wave ultra- Approximately 20 kg (44lbs.) of scheelite have violet radiation. The California specimen fluo- been found at this locality to date. Although most resced a very strong blue. A yellowish fluorescence of the crystals range from 0.30 to 5.00 ct, stones as at one end of the Mexican scheelite masked the large as 25 ct have been recovered. intensity of the typical whitish blue fluorescence. Cannon and Grimaldi (1942)proved that the yel- GEMOLOGICAL PROPERTIES low fluorescence seen in scheelite is often caused Table 1 gives the gemological properties of 10 by the presence of powellite (CaMo04)molecules. scheelites from Sri Lanka, one from California, and one from Mexico that were examined for this Spectroscopic Analysis. The visible-light absorp- study. tion spectra of scheelites from Sri Lanka, Mexico,

TABLE 1. The physical properties and reactions to ultraviolet radiation of natural scheelites from Sri Lanka, the United States, and Mexico, \

Gem locality Color Refractive Specific Short-wave ultraviolet Long-wave ultraviolet (no. of stones) index gravity

Sri Lanka (8) Colorless 1.920-1.922 5.94-6.30 Distinct whitish blue Dull oily yellow and 1.930- 1.935 Sri Lanka (1 ) V. 11. yellow 1.921 and 1.933 Distinct whitish blue Dull oily yellow Sri Lanka (1) Grayish white 1.920 and 1.935 Distinct chalky blue Dull oily yellow United States (1) Colorless 1.918 and 1.936 Very strong blue Dull oily yellow (Kern County, California) Mexico (1) Canary yellow 1.930 6.1 1 Distinct whitish blue Indistinct (Milopilos, Sonora) with yellow rims

Notes and New Techniques GEMS & GEMOLOGY Fall 1986 167 400 500 600 700 800 nm Figure 2. The absorption spectra as seen with a Wavelength prism-type hand-held spectroscope in scheelites from (a) Sri Lanka, (b) California, and (c)Mexico. Figure 3. The spectrum of a Sri Lankan scheelite as recorded on a Pye-Unicam SP8-100 UV-VIS spectrophotometer. and the United States vary considerably. The absorption spectra of some of the stones tested, as seen through a prism-type spectroscope, are shown microscope, no characteristic mineral inclusions in figure 2. The spectrum of a Sri Lanlzan scheelite were discovered, although many forms of finger- as recorded on a Pye-Unicam SP8-100 UV-VIS print-like liquid inclusions were often visible (fig- spectrophotometer is shown in figure 3. ure 6). California scheelite typically contains distinct Microscopy. The photomicrograph shown in fig- two-phase inclusions. The yellow scheelite from ure 4, taken while the stone was immersed in Sonora, Mexico, contained fine fingerprint-like methylene iodide, clearly reveals the angular zon- liquid inclusions as well as healed "fingerprints." ing frequently seen in Sri Lanlzan scheelites. Wavy kaleidoscopic colors were evident when the stone CHEMICAL ANALYSIS was observed with polarized light (figure 5). This Chemical data for the 10 Sri Lanlzan scheelites phenomenon may have been due to internal strain were obtained through energy-dispersive X-ray in the structure of the Sri Lankan material. During fluorescence (EDXRF), which revealed the pres- this study, 55 scheelites were examined with the ence of tungsten and calcium (see figure 7). Silica

Figure 4. The angular zoning seen here in a stone Figure 5. This colorless scheelite from Sri Lanka, immersed in methylene iodide is frequently ob- observed with crossed polarizers, displays the served in scheelite from Sri Lanka. Transmitted wavy kaleidoscopic effect often seen in this ma- light, magnified 40 X. terial. Magnified 50 x. 1

168 Notes and New Techniques GEMS & GEMOLOGY Fall 1986 COUNTS

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Figure 7. Energy-dispersive X-ray fluorescence Figure 6. Fingerprint-like liquid feathers are often spectrum of a Sri Lankan scheelite. The major seen in Colombage-Ara scheelite from Sri Lanka. elemental peaks, calcium (Ca)and tungsten (W), Dark-field illumination, magnified 32 X. have been labeled. was detected in most of the samples studied. A few ity, spectrum, andinclusions. Although this findis of the Sri Lankan scheelites also contained iron, gemologically interesting, the Precambrian Sri copper, and sulfur. Notably, the light yellow Lanlzan scheelite deposits have not proved to be scheelite; ,contained iron, which probably con- economically important. The small-scale mining tributes to! their coloration. Under normal operat- that produced the stones found to date has now ing conditions, Sri Lanlzan scheelite tends to split come to a virtual halt. under the electron beam of the microprobe. How- ever, patient and careful use of the microprobe provided major element percentages of CaO (20.22 RFFERFNrES wt.%) and WO3 (77.78 wt.%), but minor elements Arem J.E. (1977) Color Encyclopedia of Gemstones. Van (the remaining 2 wt.%) were not recorded. Nostrand Reinhold Co., New York City. Areall (2.0.Ir. I19431 Scheelite occurrences in Colorado. Mines SUMMARY AND CONCLUSION ~uguzin~,vol. 33, pp. 3 13 -3 14. cannon R.S. Jr., Grimaidi F.S. (1942)New method for determi- The first scheelites reported from Sri Lanka have nation of molybdenum in scheelite. Credited in the U.S. been found in a small pegmatite vein near the town Department of the Interior press notice no. 611, released of Colombage-Ara. ~ithou~hrelatively few stones ~uly16, 1942. Munasinghe T., Dissanayake C.B. (1981) The origin of have been found to date, the material is attractive gemstones of Sri Lanka. Economic Geology, Vol. 76, pp. and some fairly large pieces (up to 25 ct)have been 1216-1225. mined. Tweto 0. (1960)Scheelite in the Precambrian gneisses of Colo- rado. Economic Geology, Vol. 55, pp. 1406-1428. The Colombage-Ara scheelites differ Webster R. (1976) Gems-Their Sources, Descriptions and stones from California and Mexico in specific grav- Identification, 3rd ed. Butterworths, London.

Notes and New Techniques GEMS & GEMOLOGY Fall 1986 169 EDITOR C. W. Fryer GIA, Santa Monica CONTRIBUTING EDITORS Robert Crowningshield LAB NOTES Gem Trade Laboratory, New York Karin N. Hurwit Gem Trade Laboratory, Los Angeles Robert E. Kane Gem Trade Laboratory, Los Angeles

Fused AMBER The Fall 1983 Gem Trade Lab Notes column reported on a necklace of beads composed of sizable chunks of amber embedded in plastic. Figure 1 shows a similar necklace that was recently submitted to the New Yorlz laboratory. However, the beads in this neclzlace proved to be made from chunks of amber that were somehow fused together without the use of any identifiable cement or other binder. Many of the beads exhibited black, irregular inclusions at the contact surfaces where the fragments were fused together (figure 2). These beads were apparently manufactured by a process different from that used to produce the pressed amber that we usually see, a process by which pieces of amber are reduced to tiny fragments and then pressed Figure 1. The beads in this necklace (31 x 26 x 24 mm) appear to be through a sieve-like apparatus. This composed of chunks of amber that have been fused together. results in a fairly clear product, but one that has a "cream-of-wheat" tex- ture when viewed with magnifica- structure, which dictates in what Figure 2. Black inclusions of an tion. In addition, tiny bumps corre- directions the stones may be cleaved unknown nature occur at the sponding to the individual fragments or sawed. The somewhat recent in- contact surfaces of the fused are visible on the surface of this ma- troduction of lasers into diamond fragments in the beads shown terial in reflected light. None of the cutting has provided an effective al- in figure 1. Magnified 1 0 X. beads in the necklace shown in fig- ternative. Without applying any ure 1 had either of these characteris- pressure on the diamond being fash- tics. RC ioned, the laser can part the stone regardless of its crystalline structure, sometimes much faster and more economically than by traditional DIAMOND methods. Even problematic dia- Fanciful Cuts Created by monds, such as those with knots or Laser Sawing disoriented internal grains, can be Until just a few years ago, diamonds laser sawn in virtually any direction. were parted by one of two methods: In addition, the laser technician can cleaving or sawing. Both of these cut diamond rough into predeter- methods have specific limitations mined designs without regard to caused by the diamond's crystalline orientation.

170 Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 Over the past few years, diamonds have appeared in many ornate shapes, such as butterflies, fish, horse heads, trees, and flowers (the Spring 1986 Gem Trade Lab Notes shows a complete alphabet of faceted diamonds cut by laser]. Generally, these fancifully cut diamonds are faceted on both crown and pavilion surfaces. The Los Angeles laboratory recently had the opportunity to examine several interesting fancy-cut diamonds somewhat different from those seen previously, including a sail boat (12 mm long x 2 mm thick) and a tennis racket matched up with a baguette diamond for the handle (figure 3). Both were cut from thin macles, thereby producing relatively large stones from difficult to cut Figure 3. With the technology provided by laser sawing, fanciful cuts pieces of rough. For each item, the such as this 12-mm sailboat and tennis racket can be obtained from large parallel faces of the macle were otherwise difficult to cut pieces of rough. first polished flat and the outline of the shape cut with a laser. The grooves wete then cut into the back such stains could be artificially irra- termined" report. On occasion, the of the pie.cd,, and facets were placed diated to darken the color or produce laboratory has advised cutters to around the edges on both the top and a light to dark green color. leave a little of the colored surface on the bottom. These diamonds are Sometimes the heat of polishing the finished stone if it is one of the somewhat reminiscent of the "pro- will alter the green "skin" color to rare pieces of green rough that retains file cut" diamonds introduced in brown. This evidently occurred on some of the color after cutting. 1961. R K the stone shown in figure 4, where a One example of green surface ir- tiny brown natural irradiation stain radiation staining that left no doubt Natural-Color Light may be seen at the culet. The stone as to the natural origin of the surface Green Diamonds was graded "very light green," with a color is shown in figure 5. The 2.35- Although the presence of small green statement to the effect that the pres- ct rough crystal was very kindly or brown irradiation stains on the ence of an irradiation spot indicates loaned to us for study by a New ~ork surface of light green diamonds (usu- natural color. diamond dealer. It is difficult to ally in or near naturals) does not Nearly all diamonds cut from imagine what conditions within the automatically prove that the color is the green "speculative" rough sold natural, it is a strong indication. We by the Diamond Trading Company know of no such stains being pro- are considered speculative because Figure 4. Irradiation stains on they usually do not remain green duced artificially. It is important to green diamond rough are after being cut; rather, they end up note, however, that while these irra- sometimes altered to brown, as being in the near- colorless "G-HI1 diation stains are most probably of seen here, by the heat of polish- range. The thin green "skin" effec- natural origin, they do not prove that ing. Magnified 20 x. the "body color" of the diamond is tively masks the true body color. entirely of natural origin. Near-col- Very rarely, one of these stones turns orless or faint green diamonds with out to be faint to light green even if all surface evidence of the green skin is removed. Since the color is due to irradiation and, in most cases, no tests exist to distinguish between Editor's Note: The initials at the end of each natural and man-induced irradiation, item identify the contributing editor who stones of this color but without a provided that item. green- or brown-stained natural are 0 7986 Gemological Institute of America saddled with a "color origin unde-

Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 171 earth could have caused this dendritic surface pattern. The rough would probably cut a near-colorless stone, although it is hoped that it will not be cut, since in its present state it is a true phenomenon of nature. RC Unusual Inclusion in Diamond The same dealer provided us with another "mind blower" in the form Figure 8. At 63 x magnification, of a sawed diamond crystal fragment. the yellowish cement that joins Looking through the stone toward the two jadeite layers shown in the sawed area, one can see what ap- figure 7 is visible. pears to be a large green crystal in- Figure 7, This 20 x 6 x 2.5 mm elusion that was obviously the rea- assembled ofa son for dividing the diamond at that t17jn (0.1 mm)layer ofgreen point. However, upon turning the jadeite on top ofathicker piece over, one sees that the "in- (2.2 -2.3 mm) layer of eluded crystal" is really a negative jadeite, as evident in this crystal with a green lining (figure6). double-exposurephoto~ To add even more to the uniqueness of this specimen, inside the green- lined negative crystal is a tiny green Jadeite JADE Doublet diamond crystal that is completely loose within the cavity. RC; Figure 7 shows an oval tablet (20 x 6 Figure 9. The top portion of the x 2.5 mm) that the Los Angeles lab assembled jadeite piece is a received for identification. Simple mottled green with numerous observation revealed that the tablet small near-colorless veins. was assembled. The piece consisted Magnified 10 X. of two parts, one extremely thin (only 0.1 mm) green layer at the top and another much thicker (2.2-2.3 gemological testing methods. There- mm) white layer at the bottom. fore, we tested both the green and the Using high magnification, we noted white portions on the infrared spec- that the layers had been joined by a trometer. The infrared spectra of slightly yellowish cement that con- both portions matched the spectrum - tained numerous small gas bubbles of jadeite jade. We also scraped a tiny Figure 5. This unusual green (figure 8).The thin top layer was a amount of powder from each layer dendritic irradiation stain was mottled dark green with numerous for X-ray diffraction analysis. The observed on the surface of a small near-colorless veins (figure 9). diffraction patterns obtained for both 2.35-ct diamond crystal. Mag- Visually, this part of the assemblage layers matched that of jadeite jade, nified 10 X. somewhat resembled green chloro- strongly indicating that both parts of melanite. The white bottom portion the assembled stone were jadeite showed a definite crystalline struc- jade. However, at the present time Figure 6. A loose green diamond ture. We were able to obtain indis- we have no explanation for the ap- crystal is trapped inside a green tinct R.I. readings (ranging from 1.64 parent variation in the refractive in- irrudiution-stained cavity in to 1.74) on the green portion, which dices of the green portion. Further this sawed diamond section. seemed unusual. When examined analysis would be desirable. KH Magnified 15 X. with a spectroscope in both reflected and transmitted light, the green layer revealed distinct lines in the red por- Dyed LAPIS LAZULI, tion of the spectrum, suggesting that Difficult to Detect it was colored by chromium. Al- though the tests indicated that the The Los Angeles laboratory was re- top was probably natural-color cently asked to determine whether jadeite jade, we could not positively or not the lapis lazuli necklace illus- identify both layers with ordinary trated in figure 10 had been dyed. Ev-

172 Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 nizing them as cultured since there is almost always a clear-cut difference between the nacre and the nucleus. In fact, they are often divided by a black ring that is caused by the transparency of the conchiolin layer surrounding the nucleus (figure 11). In the past year or so, we have seen an increasing number of treated black cultured pearls. These treated black cultured pearls either fluoresce slightly greenish (rather than red- brown) to long-wave ultraviolet radiation, or are completely inert. Also, necklaces of these treated cultured pearls are usually uniform in fluores- .. cence, in contrast to the differing tones of their naturally colored counterparts. The greatest difference be- I*. tween the two products is in their Figure 10. The dye in these 15-mm lapis lazuli beads could not be de- X-radiographs. Sometimes difficul- tected on un acetone-soaked swab, but did show when the beads ties are presented in telling whether were carefu~llytested with hydrochloric acid. the treated pearls are cultured or natural, since the treatment effectively masks the contrast between idence of dye is most frequently en- Using a cotton swab soaked with a the nacre and the nucleus (figure 12). countered as a concentration of blue 10% solution of hydrochloric acid, In some necklaces, not even one or purple in the fractured and porous we obtained a light bluish purple black ring is visible around a nu- areas. This necklace had an unu- stain. Testing of only the purple cleus. If a silver-based or other sually large number of distinctly areas yielded more of a stain than did metallic dye is used, some of the purple areas, which were easily seen other areas of the beads. Therefore, if pearls may show an opaque white re- with the unaided eye. However, no evidence of dye is obtained with versal ring part way around the nu- when the beads were rubbed (first acetone, one should also try the di- cleus, since the metal deposit does lightly and then vigorously) in an in- lute HCl solution before concluding not transmit X-rays. RC cons~icuousarea with an acetone- that there is no evidence of dye. As soaked cotton swab, no dye appeared always when handling acids, use ex- on the swab. Since lapis lazuli is treme care with HC1. RK Figure 11. A black ring of sometimes coated with wax to hide conchiolin between the nacre dye, conceal a poor polish, or prevent and the nucleus on this dye from staining clothing or stone PEARLS X-radiograph identifies these papers (see the Summer 1981 and natural-color black pearls as Summer 1986 Gem Trade Lab Black Cultured Pearls cultured. Notes), we looked for a wax by care- When natural-color black cultured ful microscopic examination and pearls from Tahiti and, more rarely, testing with a hot point. None was from the Philippines and Okinawa, revealed. first appeared in the trade, the CIA Several years ago, the laboratory Gem Trade Laboratory tested them examined a dyed blue marble bead with long-wave ultraviolet radiation. which when tested with acetone did By comparing the fluorescence color not show any evidence of dye. How- with that of a polished shell from ever, when that marble bead was Tahiti, we became familiar with the tested with a solution of 10% hydro- characteristic indistinct red-brown chloric acid. a very dark blue stain glow of the natural-color black cul- appeared on the cotton swab (see the tured pearls. We were also impressed Fall 1982 Gem Trade Lab Notes). We with the distinct appearance of these decided to test the lapis necklace cultured pearls in the radiographs. shown in figure 10 with this method. We rarely have any difficulty recog-

Gem Trade Lab Notes GEMS &. GEMOLOGY Fall 1986 173 black pearls usually show a reddish brown glow when exposed to long- wave U.V. radiation. Therefore, we were quite surprised to see that this pearl fluoresced a strong yellow. This was the first time that we have seen this remarkable color fluorescence in a natural-color black pearl. KH Blue to Gray Saltwater Cultured Pearls Recently, three 10-mm round gray 'pearls," two in earrings and the third in a brooch, were submitted to the New York laboratory (figure 14) along with several pieces that were found to contain natural pearls. These gray pearls had the appearance Figure 12. In these black culturedpearls, treatment has effectively we have long associated with cul- masked the black ring around the nucleus on the X-radiograph. tured pearls, whether natural color, dyed, or irradiated. However, we were surprised by the X-radiograph, color of this pearl was derived from which showed that each pearl had an the conchiolin layer rather than from opaque center within a shell of any organic pigments in the outer average-thickness nacre. The owner layer. It was obvious, therefore, that gave us permission to remove the the color was of natural origin and pearl from the brooch, which enabled not the result of chemical treatment. us to see by looking down the drill The X-radiograph showed numerous hole that the central material was concentric layers around a dark cen- white (figure 15) and had superficial ter, proving that the pearl was of nat- properties much like those of the Figure 13. By examining the ural origin. However, natural-color traditional French pearl cement, in- damaged area next to the prong on this 5-mm black pearl, the Figure 14. All three of the 12-mmgray culturedpearls in lab was able to determine that this pair of earrings and matching brooch were found to have the color was natural. hollow centers filled with some foreign material.

A Black Natural Pearl with Unusual Fluorescence A woman's ring set with one round undrilled pearl was sent to the Los Angeles laboratory for identification. The pearl was rather small (approximately 5 mm in diameter), but had a very attractive brownish black color with a fairly high luster. Even with- ' out magnification, a small damaged area was visible next to one prong (figure 13). Here the top layer was gone, exposing part of the conchiolin layer and the underlying nacreous layer, which appeared to be a deeper black and have a higher luster than the outer layer. We also noted that the outer layer was completely transparent. We concluded that the

174 Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 eluding the tendency to be slightly soluble to our X-ray immersion fluid. We are mystified as to how these pearls were formed. If they are indeed cultured, what was the nucleus and how was it removed? As the photograph indicates, the drill hole through which the nucleus would have had to have been removed is an opening only approximately four times the size of a normal drill hole. Possibly, the pearls were cultured around a plastic bead or some experimental material, which was later dissolved. The coincidence of having three nearly identical hollow natural pearls is too great to be believed. Blue to gray saltwater cultured pearls may owe their color to one or more of five different factors: (1)pre- colored bead nuclei that show through a transparent, fairly thin, Figure 16. The yellowish green color of this 38.47-ct tourmaline is uncolored nacre may be used; (2) very unusual. growth conditions may color the nacreous layer, at times so strongly that bleaching will not remove the As seen in figure 15, the nacre is color; (31 growth conditions may blue-gray, which indicates that the cause an abnormal deposit of dark color is either natural or due to dye, conchiolin around the bead nucleus but it is definitely not caused by ir- before growth of the nacre begins, (4) radiation or by a dark layer of conchiolin. As Dr. Kurt Nassau ob- cultured pearls (usually drilled] may Figure 17. The absorption spec- served a number of years ago, gamma be dyed, with the dye commonly trum of the tourmaline shown irradiation of saltwater cultured lodging in the zone around the nu- in figure 16 is probably due to pearls darkens only the freshwater cleus and under the nacre, and (51 the unusually large amount of bead nuclei, not the nacre. Evidently, they may be irradiated, an operation manganese in this stone. that darkens the freshwater shell natural saltwater pearls or shell will bead nucleus under the colorless not be affected bv irradiation, while nacre. freshwater shell 'will be colored, as 1.649 and a specific gravity of 3.13 noted by R. T. Liddicoat, Jr. (Gemseil are still well within the range for the Gemology, Spring 1967). RC various species of tourmaline. The Figure 15. A white cement-like stone is inert to long- and short-wave material can be seen in the drill ultraviolet radiation. Viewed with a hole of one of the cultured GEM spectroscope unit, the stone pearls shown in figure 14. TOURMALINE, Unusual Yellowish Green displayed a cut-off at about 410 nin, a Magnified 15X. strong absorption band from approx- An interesting 38.47-ct yellowish imately 418 to 420 nm, and a fainter green faceted tourmaline (figure 16) narrow band at approximately 423.5 was submitted to the Los Angeles nm (figure 17).These bands are prob- laboratory for identification. In ad- ably associated with manganese. The dition to its intriguing vivid color, stone contained liquid- and gas-filled which until recently had not been inclusions typical of many tourma- seen in gem tourmalines, this stone lines (figure 181. gave a birefringence value of 0.028, Chemical data from electron which is well above the maximum microprobe analysis of four separate typically noted for other gem tour- spots on the stone revealed an unu- malines (0.0201. However, the re- sually high level of manganese (9.2 fractive index values of 1.621 and wt.% MnO). Otherwise, the results

Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 175 Figure 19. Reddish brown Zambian tourmalines (left)are often heated to produce a yellowish green color (right). Figure 18. Two-phase,liquid and gas, inclusions similar to those found in many other found that is at least half composed tourmalines were observed in I of the "tsilaisitc" component, which the stone shown in figure 17. would require more than 10.7 wt.% Transmitted light, magnified 25 x MnO. Pure "tsilaisite" has reportedly been produced in the laboratory, and provides measurable physical and optical properties. The stone we are consistent with published tour- examined, with its high manganese maline analyses. We do not know the exact origin content, exhibits properties even of this particular gem tourmaline, more like those of the man-made "tsilaisite" than does the material but we have seen some material, Figure 20. K. Sch~netzerand H. studied by Schmetzer and Bank, and vaguely reminiscent in color as well Bank found an unusually high is closer chemically to hypothetical as in physical and optical properties, weight percentage of manga- 'tsilaisite" than any other tourrna- that originated from pegmatite nese in the greenish yellow line reported thus far. If gem "tsilais- localities along the Luangwa River Za~nbiantourmalines thcit they ite" wereat some point discovered, it Valley between Kafue and Chirundi, studied, which are similar in would be distinguishable from gem in Zambia. The partial resemblance color to the stone shown here. elbaites by its higher refractive indi- to the faceted stone described here ces, birefringence, and specific grav- leads us to believe that it is of Zam- ity. A more detailed discussion of bian origin. tourmalines that they studied (see this stone is scheduled to appear in Although some gem tourmaline figure 20) may have involved manga- an upcoming issue of the American from Zambia is heat treated to nese. Tourmalines in general contain Mineralogist. R I< change or improve the color (seefig- no more than a few weight percent- ure 19), we are convinced that this ages of MnO, but Schmetzer and stone was not heat treated because of Bank reported 6.37-6.80 wt.% MnO --- the absence of any obvious damage to in the Zambian tourmalines they FIGURE CREDITS the numerous liquid-gas inclusions studied. The photos used in figures 1,2, 14, and 15 (again, see figure 18). In 1929, Kunitz [Chen~ieder were taken by Clayton Welch. Dave In most green tourmaline, the Erde, pp. 208-251) proposed the Hargett supplied figure 4. John I. Koivula took the photomicrographs used in figures dominant coloring agent is thought name "tsilaisite" for a hypothetical 5, 6, and 18. Tino Hamrnid is responsible to be iron. However, Schmetzer and new end member of the tourmaline for figure 3. Shane McClure furnished fig- Bank (Neues fahrbuch fur Min- group, with an ideal chemical for- ures 7, 10, 13. 16, and 20. Chuck Fryer's eralogie Monatshefie, 1984 pp. mula requiring about 20 wt.% MnO. photos were used in figures 8 and 9. Bob Crowningshield provided the X-radiographs 61 -69) suggested that the spectral However, "tsilaisite" is not yet offi- for figures 11 and 12. The absorption features of the yellow to yellowish cially recognized by mineralogists spectrum in figure 17 is the work of Bob brown or greenish yellow Zambian because no natural material has been Kane. Mike Havslad supplied figure 19.

176 Gem Trade Lab Notes GEMS & GEMOLOGY Fall 1986 Editorial Forum

DYED LAPIS LAZULI One needs to recall a passage from Lewis Carroll's Through the Looking Glass: I read with great interest the Gem Trade Laboratory's experiences with dyed lapis lazuli (Gem Trade Lab "When I use a word," Humpty Dumpty said Notes, Spring 1986, p. 49). I too have had some experi- . . . "it means just what I choose it to mean- ence with this material and would like to share the neither more nor less." following with you. "The question is," said Alice, "whether you can For several years we have manufactured a reproduc- make words mean so many different things." tion of a necklace that the Metropolitan Museum of Art "The question is," said Humpty Dumpty, has in its collection. One of the components is a "which is to be master-that's all." specially cut series of lapis beads. We knew that the Dictionaries do not control the use of words. A material we received from oriental suppliers had been dictionary definition is no more than a report on how a dyed, but unlike samples received from Europe, this dye word has been used in the past and is currently being did not respond to the usual acetone swab test. Indeed, used, usually with a considerable time delay. Specialized these beadshere soaked in acetone and no change was technological terms may not reach even major dictio- seen in the !color of the bead or in the acetone solution naries for decades. itself. Words frequently have several distinct meanings, Customer complaints about blue stains on clothing some general and some used only by certain specialists. and skin prompted further tests. Although the dye was For example, the term dichroism is well known to every impervious to acetone, it readily dissolved in denatured gemologist as a change in color with orientation, partic- alcohol (a major component in most colognes and ularly in polarized light. Yet chemists use the same word perfumes). to describe a change in color, e.g., of an organic dye We now "wash" all lapis coming into our studio. solution, with either concentration or thickness-a Concentrations of the dye tend to accumulate in and completely different meaning. The term impulse has a around the holes of the beads. The color removed does specific quantitative meaning in mechanics, quite dis- not seem to change the overall appearance of the bead, tinct from the nontechnical meaning. The term cul- and this washing process has eliminated customer tured is applied to microorganisms, to education and, in complaints. a specialist's sense, to pearls. And so on. Such unex- Frederick Elessar Borgardt pected specialized meanings are included in some dic- Manager, Reproduction Studio tionaries but not in others. Metropolitan Museum of Art, NY The adjectival use of synthetic as in synthetic gemstone material, etc. (and its occasional abbreviation as a noun form)has been employed widely in gemology with the consistent meaning of man-made equivalent of "WHEN I USE A WORD . . .I' the natural (see, for example, the gemology texts by THE "SYNTHETIC CONTROVERSY Anderson, Liddicoat, Nassau, and Webster, among In his letter to Gems d Gemology (Summer 1986, p. others). Synthetics are thus contrasted to imitations, 107))Dr. W. W Hanneman objects to the use of the word pastes, fakes, simulants, and so on. While this may seem synthetic as an abbreviation for synthetic gemstone. He confusing to the novice, any specialist knowledgeable in also uses the term synthetic as synonymous with any this field readily understands the intended meaning, man-made substance, despite a long gemological (and without any danger of confusion. There does not seem to gemmological) tradition of using such a designation only be any urgent need for a change. for the man-made equivalents of a natural material. Kurt Nassau, Ph.D. Some gem synthesizers have also recently stated their Bernardsville, NJ desire to replace synthetic with cultured. Continued on p. 2 79

Editorial Forum GEMS & GEMOLOGY Fall 1986 177 PHOTOATLAS OF $175.00 price tag as a great bargain, INCLUSIONS IN this is it. GEMSTONES RICHARD T LIDDICOAT, JR. By Edward J. Gubelin and John I. Chairman of the Board BOOK GIA - Santa Monica IZoivula, 532 pp., illus.,pii bl. by ABC Edition, Zurich, Switzerland, 1986. US$175.00* PEARLS: NATURAL, REVIEWS CULTURED AND Surely the name most often associ- feffrey M. Burbank, Editor 1 ated with the use of inclusions for IMITATION gem identification, and as a guide to By Alexander E. Farn, 150 pp., illus., the paragenesis of gems and gem publ. by Butlerworth &> Co., London, materials, is that of Edward J. Gu- mineral inclusions in gems, it also 1986. US$29.95* belin. Working with him on the prep- contains three essays: one by Dr. aration of this monumental photo- Edwin Roedder on the origin of fluid This book is part of the new Butter- atlas is John I. Koivula, a remarkably inclusions, the second by Dr. Henry worth Gem Books series, which is gifted gem inclusion specialist Meyer on the genesis of diamond and aimed at providing in-depth informa- and award-winning photomicrogra- its inclusions, and a third by Pro- tion on particular gems rather than pher. The combined efforts of these fessor Dr. H. A. Stalder on the forma- surveying many or all types of gem two authors and scientists has re- tion of quartz and its inclusions. Part materials under one cover. The idea sulted in a book that is sure to three covers specific mineral, fluid, has merit, but its execution in this become a classic in the gemological and glass (remnants of silicate melts book is lacking in several important literature. that never crystallized] inclusions as ways. Both authors have impressive well as multiple inclusion "scenes." At first glance, the book has all gemological backgrounds. Dr. Gu- Part four discusses various minerals the ingredients for a first-class work. belin, of Meggen, Switzerland, was and their inclusions, and part five The author, a former director of the the first person to introduce a sys- presents inclusions found in man- London Chamber of Commerce Lab- tematic classification of gemstone made materials. The final section oratory, has had gem-testing experi- inclusions. During the course of his summarizes the work. ence that comes to only a few. The career, he has published more than The authors are not given to subject matter is of great interest 150 papers and five boolzs on gemol- verbosity, but Dr. Gubelin can be because of the current popularity of ogy, and has designed instruments positively lyrical in English, which cultured pearls, and because new and accessories to improve micros- is not his native language. However, boolzs about pearls are few and far copy. As a specialist in gemstone the 1440 magnificent photomicro- between- the last great one was The microscopy, Mr. Koivula has devel- graphs speak for themselves. Beau- Book of the Pearl, by Kunz and Ste- oned several new illumination tech- tifully reproduced and accompanied venson, published in 1908. niques, including pinpoint illumi- by interesting, concise captions, they Even today, pearls are much mis- nation and shadowing. His photo- provide the most thorough coverage understood, and up-to-date informa- micrograph of a gemstone inclusion of the subject ever accomplished. tion and research are sadly lacking. captured first place in the 1984 Perhaps to prove a reviewer's Much of our recent information Nilion International Small World objectivity, I am constrained to find about natural and cultured pearls has Competition. In addition to his edi- something to criticize. It is exceed- come from pearl growers, processors, torial res~onsibilitieswith Gems &> ingly difficult in this instance, but and dealers, which is a clear case of ~emolohhe has published more on page 76 there are two photos of a the fox guarding the hens. For exam- than 50 articles in various gemologi- three-phase inclusion in which a ple, the Japanese cultured-pearl in- cal publications and contributed to cube of halite is photographed in dustry, until very recently, has been several boolzs. different positions in a liquid- and reluctant to admit that today, about The new Photoatlas has more gas-filled cavity. The caption reads, 80% of its saltwater cultured pearls than five times as many color plates in part: "Note how the gas bubbles are harvested after one or at most as Dr. Gubelin's 1974 classic, Inter- stand out from its background in two growing seasons (approximately nal World of Gemstones. There are strong relief thanks to its much eight to 20 months), rather than the some other interesting departures higher refractive index." This must, three- to four-year period commonly from Internal World as well. The indeed, be a rare gas. accepted as fact. Similarly, the Japa- Photoatlas is divided into six parts. This book is not only beautiful nese have been loath to explain the The introduction discusses the im- (it contains roughly 13,000 square extent of the processing and treat- portance and beauty of inclusions, as inches of color photographs], but it well as the procedures of microscopy also provides a wealth of valuable and photomicrography. Part two is a information on a subject of vital This book is available for purchase at pleasant surprise since, in addition importance to gemologists. If one the CIA Bookstore, 1660 Stewart Street, to the information on the genesis of can conceive of a book with a Santa Monica, CA 90404.

178 Book Reviews GEMS & GEMOLOGY Fall 1986 ments to which most cultured pearls most pearls are induced by parasitic tone, is often rambling and hard to are subjected. The need for fresh infestation of the mollusk and rarely, follow. The editor should have helped information about pearls is clear. if ever, by a grain of sand. While this to organize and present the informa- This booli endeavors to cover idea is probably correct when applied tion more effectively, so that the most aspects of pearls, cultured to the saltwater pearl, certainly as booli would lend itself to reference. pearls, and imitation pearls, and in- opposed to the grain-of-sand myth, it Although the booli has a good cludes a brief gemological descrip- should be noted that pearls, espe- number of photographs, maps, line tion, a chapter on the origin of pearls, cially freshwater pearls, are often drawings, and tables, many of these a very brief historical perspective, an nucleated by calcareous objects, in are not especially well done, and do anatomy of the pearl oyster, a discus- the form of shell bits or shell-bearing not add much. The photos of radio- sion of the sources of natural pearls, a parasitic mollusks. graphs, intended to show the features chapter on cultured pearls, the tech- The author also does a good job which identify pearls and cultured niques of pearl identification, a dis- of presenting the techniques used in pearls, are in most instances not cussion of imitation pearls, natural- pearl identification, and proceeds sharp enough to reveal these charac- pearl pricing methods, and a final from the simplest to the more ad- teristics. chapter entitled "A Pearl Pot-pourri," vanced. His information is good, al- Finally, while the author does which includes small tidbits of though a general reader might have achieve his stated objectives of dis- "pearlobilia" that wouldn't fit any- difficulty following his explanation tinguishing between the various where else. Included also are a short of the fine points and nuances of types of pearls and cultured pearls glossary, a reading list, references, modern methods of pearl testing. A and of explaining the history and and an index. table showing the strengths and technique of the pearl-identification The author effectively works to weaknesses of each method, vis-a-vis practices used at the London Labora- clarify and distinguish the differ- the various types of pearls and cul- tory he falls short of the broader goal ences between the various types of tured pearls, would have been help- of providing a useful source of infor- pearls and cultured pearls. Although ful. The table showing the number of mation for both the public and the the point has been made many times pearls and cultured pearls tested at jewelry trade. His obvious forte is before, he emphasizes the fact that the London Laboratory from 1926 to pearl identification, especially of ori- the term pearl should only be applied 1984 is new information and very ental pearls, but the information he to natural pearls, of either saltwater interesting. Notably, the author provides about cultured pearls in or freshwater origin, and that cul- points out the difficulty in using general and freshwater pearls in par- tured pearls should always be desig- available techniques to test some of ticular, both natural and cultured, is nated as such. This is an important the newer cultured pearls, especially often out of date or incorrect. Al- distinction not always made in com- mantle-tissue nucleated cultured though the book is truly a noble merce. pearls produced in saltwater, and effort by a respected author, at a time The second chapter, on the ori- calls for ongoing research in this when our knowledge about pearls gin of pearls, takes the reader back to field. and cultured pearls is still plagued by the earliest ideas about pearl forma- The book could have been much myths, half-truths, and noninforma- tion (e.g., myth of dew-formed better in its overall execution; I came tion, the work does little to break pearls), and then carefully traces the away with the impression that it was new ground. evolution of modern thought on rather hurriedly put together. It suf- JAMES L. SWEANEY, G.G pearls which arrives at the conclu- fers from a so-so editing job: the Mardon Jewelers sion, scientifically derived, that author's writing style, erudite in Riverside, CA

Continued from p. 177 And, if Dr. Hanneman is going to be pedantic, the MORE ON "SYNTHETIC" terms borate and silicate indicate a chemical formula, not a "defined crystal structure." The possible crystal I would like to comment on the letter from W. W structure may be inferred from the formula, but equally, Hanneman in your Summer 1986 issue. many substances with a chemical formula can also exist Synthetic is acceptable on two grounds: (1)often in in an amorphous form. Australia's best-known precious the usage of the English language, the noun is inferred, stone - opal - has the formula Si02*nH20and is amor- and the adjective only expressed; (2) I know of no phous; chalcedony, with the same formula, is not. dictionary that covers the specialized usage in every field of science, arts, sports, etc. A synthetic is a term W H.Hicks, FGAA perfectly understood by all gemologists, and widely Editor, Australian Gemmologist defined in all gemological literature. South Yarra, Victoria, Australia

Book Reviews GEMS & GEMOLOGY Fall 1986 179 GEMOLOGICAL ABSTRACTS

Dona M. Dirlam, Editor

REVIEW BOARD

William E. Boyajian Mahinda Gunawardene Elise B. Misiorowski GIA, Santa Monica Idar-Oberstein, Germany GIA, Santa Monica Jeffrey M. Burbank Gary S. Hill Michael P. Roach GIA, Santa Monica GIA, Santa Monica Andin International, New York Stephanie L. Dillon Steve C. Hofer Gary A. Roskin San Clemente, California Kensington, Connecticut GIA, Santa Monica Bob F. Effler Karin N. Hurwit James E. Shigley GIA, Santa Monica Gem Trade Lab, Inc., Los Angeles GIA, Santa Monica Emmanuel Fritsch Robert C. Kammerling Franceye Smith GIA, Santa Monica GIA, Santa Monica GIA, Santa Monica Joseph 0. Gill Neil Letson Carol M. Stockton Gill & Shorten Ltd., San Francisco Palm Beach, Florida GIA, Santa Monica Fred L. Gray Shane F. McClure Sally A. Thomas Richter's, Georgia Gem Trade Lab., Inc., Los Angeles GIA, Santa Monica

COLORED STONES AND ORGANIC black), occasionally streaked or mottled with green and MATERIALS white; luster = vitreous on polished surfaces, dull to subvitreous on rough surfaces; diaphaneity = opaque; Bowesite-a new lapidary material from Australia. fracture = uneven to hackly; cleavage = none; refrac- S. M. B. Kelly, Australian Gemmologist, Vol. 16, No. tive index = 1.57; specific gravity = 2.78-3.10, the 1, 1986, pp. 5-8. higher values for darker-colored material; spectra, The author reports on a new ornamental gemstone pleochroism, and fluorescence to ultraviolet radiation = found near the town of Cracow in Queensland, Austral- none. ia. Dubbed "bowesite," the material contains widely This material is currently being used for carving. varying amounts of diopside, epidote, grossularite gar- RCK net, actinolite, andesine feldspar, quartz, sphene, calcite, and an iron oxide (probably magnetite]. Emeralds. H. de Santana, City o) Country Home, Vol. 5, The gemological properties of "bowesite" are as NO. 3, 1985 pp. 112-122. follows: color = green, from light to very dark (almost Aimed primarily at more knowledgeable consumers, this article is meant to be a "primer" on emeralds. It flows through emerald folldorc, history, and gemology, This section is designed to provide as complete a record as and concludes with a few cautionary tips on how and practical of the recent literature on gems and gemology. Articles are selected for abstracting solely at the discretion ol the section where to buy emeralds and what to look out for in editor and her reviewers, and space limitations may require that emerald fakes, treatments, and synthetics. we include only those articles that will be of greatest interest to our Although most of the information should be famil- readership. iar to the jeweler/gemologist, de Santana does present Inquiries for reprints of articles abstracted must be addressed to several interesting nuggets. For example, he reveals how the author or publisher of the original material. the Spanish traded their glut of newly discovered Co- The reviewer of each article is identifiedby his or her initials at the lombian emeralds to the Moghul princes of India, who end of each abstract. Guest reviewers are identified by their full were eventually robbed of their treasures by the Per- names. sians. In this way, many spectacular Colombian emer- 01986 Gemological Institute ol America alds were incorporated into the crown jewels of Iran and

- the coffers of other Middle Eastern countries.

180 Gemological Abstracts GEMS & GEMOLOGY Fall 1986 Color photos of magnificient emerald crystals and ebehandlung (Solid solution of iron and titanium jewelry accompany the text. SAT for explaining the blue colour of rutile- and spinel-containing silky-milky corundum after heat Les gemmes en lumi6re (Gems in light). C. da Cunha treatment.) H. Harder and A. Schneider, Neues and A. da Cunha, Monde et Mineraux, No. 73, fahrbuch fur Mineralogie Mona tshefte, No. 5, 1986, 1986, pp. 27-29. pp. 209-21 8. In this second in a series of articles that uses diverse The treatment of gemstones, especially corundum, has specific examples to educate about gemology, the au- become a growing concern to the trade in recent years, thors discuss three stones: a color-change sapphire, a The authors report that heat treatment to produce blue sinhalite mistaken for a zircon, and, most interestingly, sapphires is usually undertaken on nontransparent, a blue sapphire from Ceylon that contains a new type of heavily included grayish corundum from Sri Lanka. The inclusion. When viewed with 40 x magnification, the blue color appears during heating, along with a striking inclusion resembles the pattern seen in nylon hosiery improvement in transparency. However, clear sapphires (with one run!).This striking new feature is illustrated seem to lose their color by the same process. This is by a color photograph. Although this is the only stone in related to dissolution of rutile needles in the corundum which the authors have seen such a pattern, they matrix at temperatures above 1550Â°C speculate that this may be a characteristic inclusion of a The origin of the blue color in natural sapphires has natural stone. EF previously been attributed primarily to intervalence charge transfer between Fe2+ and Fe3+, although we Irradiated gems: why the color comes and goes. K. know that the blue in synthetic sapphires is due mainly Nassau, Jewelers' Circular-Keystone, Vol. 157, No. to Fe3+-Ti4 + charge transfer. To understand the origin 7, 1986, pp. 294-299. of the heat-induced color, the authors investigated iron- In this article, Dr. Nassau clarifies how the irradiation bearing inclusions in a sapphire from Sri Lanka with an process relates to color changes in certain gemstones. electron microprobe. Rutile needles were observed The reason behind these color changes is color centers, a which were found to contain up to 30% iron in both concept that pr. Nassau simplifies well for the reader. valence states. An Fe- and Mn-rich phase, probably Because color centers vary in strength from one material spinel, was also found. The corundum contains 0.1 % to anothei irradiation-oroduced color is stable in some FeO and 0.005% TiO,. and not stable in others. The author then After a 30-minute treatment at 1600Â¡C the co- explains hob different types of irradiation produce rundum was found to contain about the same percentage different results. The two major irradiation processes are of iron oxide but 0.17% Tioil a 30-fold increase. discussed, with disadvantages and advantages of each Titanium in lower concentrations was found in the process. vicinity of former rutile inclusions. This clearly demon- The first process uses either X-rays or gamma rays. strates that rutile inclusions are dissolved and titanium Gamma-ray facilities produce uniform coloration with- diffused away during the heating process. Iron appears to out generating any significant heat or other hazard, such be mobile as well, but it reappears in the form of other as radioactivity. X-rays behave much like gamma rays, types of inclusions (such as magnetite) on cooling, and but they produce color less uniformly and more slowly. does not remain diluted in the corundum host. The The second major process involves high-energy elec- magnesium is not mobile. trons or neutrons. High-energy electrons are produced in Unfortunately, an optical absorption spectrum is linear accelerators by means of a process that consumes not available. However, it is hypothesized that the considerable electricity and can produce intense lo- increase in available diluted titanium after heat treat- calized heating. Flowing cold water is needed to keep the ment is responsible for the blue coloration. Therefore, gemstones from melting. Neutrons in a nuclear reactor this is an example of a Fe2+-Ti4+ charge transfer. EF produce uniform color without localized heating. Both electrons and neutrons can induce radioactivity, so On the origin of blue sapphire from Elahera, Sri Lanka. gemstones may need to "cool off." G. Heilmann and U. Henn, Australian Gemmolo- The author also exvlains how to tell whether a color gist, Vol. 16, No. 1, 1986, pp. 2-4. produced by irradiation is stable or will fade. A section In this report on light blue sapphire found near Elahera on the materials that are commonly irradiated is includ- in the Central Province of Sri Lanka, the authors ed, along with a convenient table summarizing the describe the geology of Sri Lanka and the Elahera area treatments and their stability. The article is well written specifically, and then present chemical data from elec- and easy to understand. David C, LeRose tron microprobe analyses of the samples studied. Thesc data show color-causing iron and titanium contents Isomorpher Einbau von Eisen und Titan zur Erklarung comparable to those of sapphires from other Sri Lankan der blauen Farbe von Rutil- und Spinell-haltigen sources. seidig weifsen Korunden nach einer Warm- Examination of the sapphires with a microscope

Gemological Abstracts GEMS & GEMOLOGY Fall 1986 181 revealed the following: feathers consisting of elongated cation. Other gems mentioned in this article include liquid-filled and two-phase inclusions, oriented rutile liornerupine, sinhalite, manganotantalite, alexandrite, needles, rounded zircon crystals with pleochroic halos, sapphirine, demantoid, cassiterite, iolite, and triphane prismatic apatite crystals, and platelets of biotite mica spodumene. David C. LeRose that show areas of severe corrosion. Based on the nature of the mica inclusions, the authors conclude that the DIAMONDS sapphires originated from garnet-bearing gneisses that form the ridges bordering the gem pits. R CK Famous diamonds of the world (XXIV): the "Nassakff diamond. I. Balfour, Indiaqua, Vol. 42, No. 3, 1985, Possibilities and limitations in radiographic deter- pp. 133-135. mination of pearls. I. Lorenz and K. Schmetzer, According to Balfour, a 90-ct stone known as the Nassak Journal of Gemmology, Vol. 20, No. 2, 1986, pp. originally graced a statue of the god Shiva that stood in a 114-123. Hindu temple in the town of Nasik, India. When the In the introduction, the authors briefly cover the investi- British defeated the last Indian Peshwa in 1818, the stone gations of other authors who have previously worked on came into the possession of the Marquess of Hastings, the different methods of identification of pearls, fresh- or who in turn presented it to the East India Company. saltwater, natural or cultured. An outline of the experi- They handed the precious stone over to the firm of mental details used in this project is then given, includ- Rundell and Bridge, who had the awkwardly cut stone ing a list of the number of necklaces or individual pearls recut for greater brilliance with only a 10% weight loss. the authors tested and the testing parameters for each In 1831, Emanual Brothers bought the Nassak for different method. only Â£7,20 (the low figure has been attributed to the Results of the X-radiographs, X-ray diffraction depressed financial conditions during that period). In (Lauk) patterns, and X-ray luminescence are discussed 1837, the Nassak was sold at auction (along with the and combined in capsule form in a table. However, there Arcot and King George diamonds) to the first Marquess appears to be an error in the table, where the authors of Westminster, and it remained in the family until 1926 state that there is a radio-opaque bead in the center of when it was sold to Georges Mauboussin, a Paris jeweler. bead-nucleated cultured pearls. Beads used for nuclei are Subsequently, the Nassak was purchased by Harry usually made out of freshwater shell, which is translu- Winston, Inc., of New York, who had it recut to its cent to X-rays, not opaque. While the beads are not as present 43.38 ct. The stone went through the hands of transparent to X-rays as conchiolin is, they are far from three more owners until 1977, when it was sold to the opaque, and are actually very slightly less transparent to King of Saudi Arabia. SAT X-rays than is saltwater nacre. In their discussion of the various X-ray testing Latter-day origin of diamonds of eclogitic paragenesis. methods, the authors point out what they feel are the S. H. Richardson, Nature, Vol. 322, No. 6080, 1986, advantages and disadvantages of each test. They con- pp. 623-626. clude by giving a schematic diagram which proposes a Mineral inclusions of syngenetic origin in diamonds plan to determine the identity of a pearl of unknown (inclusions that formed contemporaneously with the origin. C. W Fryer diamond)provide a means of determining the conditions of diamond formation. The mineral inclusions in dia- Rare among rare. J. C. Zeitner, Lapidary Journal, Vol. 39, mond fall into two groups: (lJ a group consisting of NO. 12, 1986, pp. 26-34. olivine, orthopyroxene, and chrome pyrope, referred to This article capsulizes the properties, history, and some as the "peridotitic" paragenesis; and (2)a group contain- interesting facts about the more unusual gems of Asia. ing pyrope-almandine and omphacitic clinopyroxene, The author has classified these gems as rare using as her known as the "eclogitic" paragenesis. Inclusions of both criterion the fact that only a few specimens are known groups can be age dated by any of several isotope dating (such as painite), or that the material is a rare variety of a methods. Using samarium-neodymium isotope ratios, more common species (such as imperial jadeite). Not diamonds of the peridotitic paragenesis from the Kim- only does the author discuss gems that have been used berley and Finsch kimberlites in southern Africa were for centuries (despite their rarity), such as cat's-eye dated at approximately 3.3 billion years. In contrast, chrysoberyl and "padparadscha" sapphire, but she also diamonds of the eclogitic paragenesis, which predomi- describes the more recent discoveries of painite and nate at the Premier kimberlite in southern Africa and taaffeite. Included in the article is a spectacular multi- the Argyle lamproite in northwestern Australia, have star variety of quartz found in Sri Lanka -as many as 16 much younger ages of 1.1-1.2 billion years. Thus, the stars have been observed on one gem. Another stone diamonds in the latter group represent a second, genet- discovered in Sri Lanka, cat's-eye zircon, has an unusual ically distinct origin as compared to the much more chatoyant eye caused not by rutile but by tightly packed ancient group of diamonds with "peridotitic" inclusions. bands of mineral flakes, which are visible under magnifi- The origin of diamonds in the second group is related in

182 Gemological Abstracts GEMS & GEMOLOGY Fall 1986 time and space to periods of lzimberlite or lamproite creased in Australia, Angola, South Africa, Liberia, and magmatism. IES Namibia. Production figures for South America, the People's Republic of China, the USSR, and a few other The rarest gem. D. Kaye, Town o) Country, Vol. 140, No. countries are only estimates due to the difficulties in 5073, 1986, pp. 134-139, and 177. obtaining reliable information. Fancy colored diamonds, which are among the rarest of The author's comprehensive style, augmented by all gemstones, have never before enjoyed such popu- graphs, makes this a fine overview of an important larity and awareness as they do today. In the case of subject. EBM natural-color diamonds, the increased awareness of their breathtaking beauty and rarity has created unprece- dented demand and unparalleled prices. The author presents a lively story of today's colored GEM LOCALITIES diamond market, reflecting on the experiences and personal opinions of several dealers and collcctors who A bibliography of general mineral locality publica- specialize in these spectacular gems. tions for the United States and Canada. R. D. A brief explanation of the chemical make-up of Titamgim, Rocks o) Minerals, Vol. 61, No. 4, 1986, diamonds acquaints the reader with the cause of color in pp. 203-209. these stones. The artificial coloring of diamonds by The gem and mineral collector can make his field trips atomic bombardment is also mentioned. A brief account much more rewarding by finding reference to locations of yellow, pink, blue, and brown diamonds familiarizes that have already produced the minerals that interest the reader with historical notes, mining locations, and him. Here Titamgim discusses how to research lo- descriptive terms associated with these color varieties. calities through the literature. An annotated bibliogra- A discussion based on several interviews with phy of publications that describe gem and mineral dealers and gemologists regarding the judgment of color localities in the United States and Canada (listed by in these gems concludes that color discrimination is a state or province inUadditionto general references)is the difficult process that requires years of experience to focal point of the article. Many of these publications in develop. Current grading practices are also discussed, turn include bibliographies that will provide additional and their strengths and weaknesses identified. sources of information. Barton C. Curren Despite a few minor errors and omissions, the article is very interesting reading. It is well illustrated Locating gem deposits by computer. M. O'Donoghue, with 20 color photographs of colored diamonds set in a Journal of Gemmology, Vol. 20, No. 2, 1986, pp. spectacular array of jewelry pieces. SCH 87-90. O'Donoghue presents an excellent introduction on how Rise in output: mining the same but officially reporting computer-searchable databases can aid the gemologist more. J. Roux, Jewellery News Asia, No. 19, 1986, in locating gem-locality information. He begins with a pp. 39-47. review of the printed sources of information on gem It is difficult at best to compile figures for world deposits, commenting briefly on geologic maps. Then he production of diamond rough. In some countries these turns his attention to strategies for computer searches in statistics are unobtainable, and in others the activities two earth science bibliographic databases: GEOREP and of illicit miners and smugglers make accuracy impossi- GEOARCHIVE. ble. Nevertheless, using statistics from the United States Performing computer searches is like mastering a Bureau of Mines and the Mining Annual Review, Mr. new language, with a new vocabulary to learn and new Roux presents as detailed an analysis of the current rules to follow. O'Donoghue points out some of the most diamond production as possible. essential of these rules, including spelling, truncation, The report, broken down by continent, country, and Boolean logic, as he discusses specific gem localities and, where applicable, individual mines, lists the output such as the ruby mines in Mogok, Burma. By carefully of diamond rough for 1983 and 1984, and the reasons for studying this article, the reader can learn some of the increases or decreases in each case. For example, in difficulties encountered in doing computer searches. Botswana, a better grade of ore (where grade equals the OIDonoghue concludes his article with two of the number of carats obtained from 100 tons of ore) is most challenging variables, geographical coordinates responsible for the increase in production from the and chemical data. It is important to emphasize a Jwaneng mine. In Angola, the war between the UNITA caution the author touches on early in the article: rebels and the existing Angolan government plus the Databases can be expensive to use. To avoid unnecessary high incidence of diamond smuggling are responsible for costs, one must be well prepared before beginning a the drop in production. computer search. A good way to begin is to ask a Essentially, production increased in Botswana, the librarian trained in database searching for assistance. Central African Republic, Guinea, and Zaire; it de- DMD

Gemological Abstracts GEMS & GEMOLOGY Fall 1986 183 Peridotites from the Island of Zabargad (St. John), Red Woods and Collins present the various causes of the Sea: petrology and geochemistry. E. Bonatti, G. yellow color in diamonds, as they describe the effect of Ottonello, I? R. Hamlyn, Journal of Geophysical radiation damage and annealing. New criteria for the Research, Vol. 9 1, No. B 1, 1986, pp. 559-63 1. identification of treated yellow diamonds are proposed The small island of Zabargad, in the Red Sea, has long on the basis of sharp infrared absorption bands that been known as a source of gem-quality olivine, or appear after a diamond has been both irradiated and peridot, which occurs in mantle-derived rock known as annealed: the H,,, and HI=lines (at 2024 and 1935 nm, peridotite. Despite the historic notoriety of this island, respectively). These lines may be eliminated by heating there have been few detailed studies of its geology. This the stone to 1400Â°Cbut the result is a very unattractive article presents results of a recent detailed study of the green color and graphitization of the inclusions. Zabargad peridotites that was undertaken to document In general, a treated stone should exhibit either the their geologic features and establish their origin. 595-nm line or the Hi,, and Hi- lines. The presence and Bodies of peridotites crop out at several locations on intensity of other bands (Hi, HA. 1450 cm-1) may help the island. The peridotites can be divided into three confirm the diagnosis. With such criteria, no treated groups: (11 a spinel lherzolite containing olivine, ortho- yellow diamond should be mistaken as naturally col- pyroxene, clinopyroxene, and spinel; (2)amphibole peri- ored. However, a yellow diamond that the late Basil dotites, with some magnesiohornblende in addition to Anderson had purchased before 1950, and which he was the group of minerals mentioned above, and (3) pla- certain was natural, exhibits the features of an irradiated gioclase peridotites that contain plagioclase along with and annealed stone. Consequently, the authors conclude the other four minerals. Detailed mineralogic and geo- that a natural color yellow diamond could very rarely be chemical data are presented for each rock type. All three classified as treated. EF rock types were derived from peridotitic melts that originated in the upper mantle at depths of approx- JEWELRY ARTS imately 30 lzm. The melts were probably emplaced from the upper mantle into the crust during the development Goldsmithing for profit. A. Revere, Jewelers' Circu- lar-Keystone, Vol. 156, No. 13, 1985, pp. 120-124. of the~edSea rift zone,, in post-~esizoicA time. Gem-quality olivine crystals are usually found in The title of this article is somewhat misleading, since it sizes up to 1 cm, although larger pieces have been mined. does not reveal money-making techniques for estab- They are principally found in one area on the south side lished goldsmiths. It does, however, contain step-by-step of the island, near a major fault along which a zone of instructions for making two pieces of jewelry as out- alteration of the peridotite has developed. These gemmy lined by Alan Revere, instructor at the Revere Academy crystals appear not to have been formed by the same of Jewelry Arts in San Francisco, California. process of melt crystallization that resulted in the The first project instructs beginning goldsmiths on formation of olivine and other minerals of the peridotite. how to make a pearl ring, covering the basics of sawing Rather, the gem olivines probably crystallized as a result and filing, as well as measuring, soldering, and finishing. of the reaction of a volatile-rich hvdrothermal fluid and The second project, a cylinder box clasp, requires a more the already crystallized peridotite. These reactions are advanced expertise in these techniques. Both projects thought to have taken place at temperatures in excess of are accompanied by helpful photos and notes. SAT 50PC but at relatively low pressure. JEs Indian antiquity. l? Francis, Jr., Lapidary Journal, Vol. 39, No. 12, 1986, pp. 45-55. INSTRUMENTS AND TECHNIQUES Although this article contains a plethora of information New developments in spectroscopic methods for de- about Indian amethyst and citrine (including folklore, tecting artificially coloured diamonds. G. S. Woods geology, trade between India and Rome, and heat treat- and A. T. Collins, Journal of Gemmology, Vol. 20, ment), it is primarily focused on the ancient lapidary NO. 2, 1986, pp. 75-82. centers of Kotalingala and Arilzamedu. Much of the In this article on the separation of natural from treated information is based on recent archaeological excava- (i.e.,irradiated and heated) yellow diamonds, the authors tions of the sites. describe the importance of sophisticated equipment. Kotalingala, located on the Godavari River in cen- They focus on the UV-spectrophotometer (which pro- tral India, thrived from the fifth to the first century B.C. vides a graph of the spectra), coupled with a cryogenic Although Kotalingala was a major regional trade city unit to cool the diamond and sharpen absorption bands, and was known for its amethyst and agate beads, it does as well as an infrared spectrometer. We now know that not appear that the beads produced there were traded out the 595-nm absorption line ("5920"), once thought to be of the country. The lapidaries in this city made only characteristic of treated stones, is destroyed when the relatively simple round, cylindrical, or barrel-shaped diamond is heated at about 1000Â°Cas a consequence, beads. Careful excavation of a Kotalingala lapidary shop some treated yellow stones do not show this band. revealed that it was a small operation that required only

184 Gemological Abstracts GEMS & GEMOLOGY Fall 1986 four basic tools, and probably employed only one or two Sophisticated ladies-what seven smart jewelry shop- workers. Since very little citrine has been recovered pers really think about you. S. Jensen, Modern from this site, experts believe that Kotalingala lapidaries Jeweler, Vol. 85, No. 5, 1986, pp. 37-43. did not know how to heat treat amethyst to create This article is an interview with a panel of seven women citrine. who frequently purchase fine jewelry from retail outlets. In contrast, the slightly more recent city of Ar- They express their likes, dislikes, and what, if possible, ilzamedu, located on India's southeast coast, was much they would change in retail operations. more involved in foreign trade, especially with the These women have a strong desire to be educated by Romans. This city boasted several different lapidary their jeweler about the jewelry and gemstones they shops, which produced a dazzling array of both glass and purchase. They are discouraged by quiet showrooms stone beads. The Arikamedu lapidaries were far more with high-pressure sales personnel, preferring to be advanced technologically than those of Kotalingala, as greeted and left to browse and ask questions at their revealed by their extremely fine, uniformly shaped leisure. The panel expects certain services from their beads, pierced with diamond-tipped drills. The great jeweler such as the cleaning and inspection of their number of citrine fragments recovered from the Ar- jewelry. They expect problems to be brought to their ilzamedu lapidary shops indicates that these lapidaries attention before they turn their jewelry in for repair or may have been skilled at creating citrine from amethyst. cleaning. A store that employs an imaginative designer SAT who can accurately sketch and describe the finished piece of jewelry is also important. They are not opposed JEWELRY RETAILING to purchasing gold and silver from discount stores, but they prefer to purchase gemstones from their established The refashioning of Zale. S. Jensen, D. Federman, and J. jewelers. All are put off by advertising that insults their Thompson, Modern Jeweler, Vol. 85, No. 7, 1986, pp. intelligence. 100-123. This article presents excellent insights into the Zale Corporation has undergone enormous changes desires and expectations of some important customers. during the'past two years, and three Modern Jeweler Catering to the needs of these customers will lead to editors sp.edt a week interviewing company officials and increased popularity and, more importantly, increased former employees to find out why. This special report sales. Barton C. Curen delves into, Zale's new corporate strategy, their new breed of executives, and the upscale Bailey Banks & SYNTHETICS AND SIMULANTS Biddle division. Also included are interviews with Zale Chairman Donald Zale and President Bruce Lipshy, and Natiirliche kobaltblau Spinelle von Ratnapura, Sri a synopsis of Peoples Jewelers' attempt to overthrow the Lanka (Natural cobalt blue spinel from Ratnapura, megaretailer. Although much of it is repetitious, this 23- Sri Lanka). H. Harder, Nezies Jahrbuch fur Miner- page article does reveal the relentless, unified force alogie Monatshefte, No. 3, 1986, pp. 97-100. behind "the golden arches of the jewelry industry." This article compares the chemical and gemological In 1984, Zale's merchandising changed from bridal properties of a set of Verneuil synthetic colbalt-colored diamonds to a wider fashion image that includes gold, blue spinels with one natural cobalt-colored blue spinel. pearls, and colored stone jewelry. On the basis of what The color in the synthetic stones is caused by cobalt (up Zale claims to be voluminous market research, the to 0.02%) or by a mixture of cobalt with chromium company is now driven by marketing rather than (0.003%], vanadium [0.001%), and titanium (0.013%). manufacturing considerations. To a man (thereappear to Verneuil synthetics almost always contain more alumi- be -no female top executives), the new generation at num than natural stones contain, and show no detect- Zale's believes that today's target consumer is the able gallium. Their refractive index range is higher fashion-conscious American working woman who now (1.719-1.730) than that of natural spinel (1.715-1.720), has the financial and emotional power to deck herself as is the specific gravity (3.63-3.64 vs. 3.58-3.61). out. According to Zale's stats, these "jewelry junkies" Irregular color zoning and strong ultraviolet fluores- are primarily interested in style, beauty, and price rather cence in the synthetic stones can be considered as than consumer knowledge, and have little loyalty to any complementary identification criteria. particular jewelry store. Interestingly, this philosophy Natural cobalt-colored blue spinel has been found conflicts with that voiced by seven women interviewed in the Paradise mining area of Sabaragamuwa Province, by S. Jensen in the May 1986 issue of Modem Jeweler, all in the Ratnapura District, Sri Lanka. The author exam- of whom were unanimous in their quest for product ined a 1.22-ct rough crystal. It showed an absorption knowledge and in their loyalty to a trusted, proven between 535 and 600 nm - like the Verneuil synthetics jeweler. but weaker -and a strong red fluorescence near 720 nm; Ultimately, only time-and profits-will tell if so, those optical criteria could not be used for identifica- Zale's "ready-aim-fire" mentality is really on target. SAT tion. But some unspecified inclusions in a cleavage leave

Gemological Abstracts GEMS & GEMOLOGY Fall 1986 185 no doubt about the natural origin of the stone. X-ray Synthesis and characterization of tourmaline in the fluorescence revealed an extremely high cobalt concen- system NazO-Al&-SiOz-B&-HzO. l? E. Rosen- tration (0.09%)as well as 0.29% iron, and 0.01% gallium berg, F. F. Foit, Jr., and V Elzambaram, American (which are almost always under the detection limits in Mineralogist, Vol. 71, No. 718, 1986, pp. 971-976. synthetics) together with 0.025% chromium and A generalized ideal chemical formula for the tourmaline 0.035% vanadium. mineral group can be written XY3Z&Si6(O, OHJao(OH, As a conclusion, the author recommends the use of F). In this formula, 'X', 'Y', and 2' represent sites of refractive index and inclusions to distinguish between different size and geometry in the tourmaline crystal natural and synthetic spinels. Surprisingly, this study structure where various cations are located. In the case

does not refer to any literature, even to the well- where X = Na + and Z =Al3+, there are the four tour- documented paper by J. E. Shigley and C. M. Stoclzton malines: elbaite (Y= A13 + + Li + ),schorl (Y= Fez + ),drav- (Gems o) Gemology, Spring 1984, pp. 34-41), which ite (Y= MgZi-), and buergerite (Y = Fe3+ 1. The authors of focused on the same subject. EF this article describe the laboratory synthesis of a similar Na-A1 tourmaline whose composition approaches that On the problems of using the gallium content as a of (Y = Al3+ ). The tourmaline formed by melt crystalliz- means of distinction between natural and syn- ation in tiny, acicular crystals up to 200 micrometers in thetic gemstones. H. Schrader and U. Henn, Journal length. Refractive indices are epsilon = 1.639 and ome- of Gemmology, Vol. 20, No. 2, 1986, pp. 108-113. ga= 1.642. The chemical and physical properties of Recent investigations of trace elements in gemstones these crystals are similar to those of elbaite and dravite. have led to claims that gallium content can be used as a The results reported in this article demonstrate the means to distinguish natural from synthetic gemstones. progress that has been made in the laboratory toward The results obtained by the authors of this article synthesizing minerals with complex chemistry. JES through neutron activation analysis of natural and synthetic emeralds, corundums, and chrysoberyls reveal that the guidelines set by previous researchers are Synthetic diamond as a pressure generator. A. Onodera, inadequate. The ranges of gallium content for natural K. Furuno, and S. Yazu, Science, Vol. 232, No. 4756, and synthetic emeralds and corundums overlap consid- 1986, pp. 1419-1420. erably, while those of chrysoberyls are close enough to Synthetic diamonds have recently become available in overlapping that they warrant extreme caution. suitable size (approxiately 1 ct] and quality for use as The authors also review the nondestructive tech- opposed anvils to generate high static pressure (up to 680 niques available for trace element determination as well kilobars). These stones have been grown by Sumitomo as the advantages and drawbacks of each. It becomes Electric Industries in Japan. They are type Ib diamonds, readily apparent that such methods are far from becom- containing singly substituting nitrogen, and therefore ing standard gemological techniques. The article con- have a deep yellow color. The nitrogen concentration cludes with a warning against reliance on gallium ranges from 30 to 60 ppm, as determined with the IR content for determination of origin and a proposal for absorption at 1130 cm-1. An X-ray topography study further research in this area. CMS suggests that they have very few extended defects. The authors claim the following advantages for the use of synthetic diamonds in high-pressure experiments: (1) Opticon! 0, Opticon! B. Jones, Rock and Gem, Vol. extended defects are fewer and can be controlled, (2)the 16, No. 7, 1986, pp. 60-61. concentration of nitrogen can be monitored to improve Opticon is the registered trademark for a prepolymer the strength, (3)the pressure-temperature conditions for plastic resin produced by Hughes Associates of Excel- preparing diamond crystals can be determined, and (4) sior, Minnesota. This resin is being promoted as filler for suitable crystals can be obtained repeatedly. (However, mineral specimens and -gemstones that have cracks or the authors do not say that the growth experiment is cavities which extend to their surfaces. Opticon has a reproducible). refractive index of 1.545, which is very close to that of Interestingly, the fracture mode of these synthetic quartz (1.544-1.553). Cracks or cavities within stones of diamonds is very different from that of natural dia- a similar R. I. will virtually disappear when penetrated monds. The cracks remain very shallow instead of by this resin. Quartz gems, such as amethyst and citrine, leading to spalling or vertical fractures. The hardness, members of the beryl group, such as aquamarine and determined by indentation ("deformation" hardness), emerald, as well as iolite and the feldspar group lend depends very little on the orientation, in contrast to themselves very well to this treatment. natural diamond, which is anisotropic. If a gem is suspected of being treated with Opticon, Although this article does not provide information

it can be tested with a hot *,noint, which will melt the on current production and price, it does give very resin filler and have no effect on the gemstone itself. interesting technical insights on the quality of Japanese Barton C. Curren synthetic diamonds. EF

186 Gemological Abstracts GEMS & GEMOLOGY Fall 1986 COLORED STONES Green-fluorescing emerald from Coscuez. An unusual emerald crystal from Coscuez, Colombia, was brought to us by Mr. Ron Ringsrud for examination. The report that follows was prepared by Dr. Emmanuel Fritsch, a GIA research scientist. The crystal, about 1.5 cm long and 0.8 cm in diameter, weighs 7.94 ct. Its refractive indices (1.578 and 1.585) and specific gravity (2.72 by the hydrostatic method) are typical of material from Colombia (see Gems o) Gemology, Summer 1986, pp. 67-79, for an in- depth article on Coscuez emeralds). The optical absorption spectrum is characteristic of that of emerald, with chromium lines around 680 nm visible with a hand spectroscope; although some features strongly suggest the presenceiof vanadium (Carol Stockton, pers. comm.]. The specimen's external structure is the result of parallel intergrowth of a bundle of smaller (1-5 mm in diameter) crystals. Strong color zoning can be seen both parallel and perpendicular to the optic axis. The color decreases from one end (dark green] to the other (colorless) of the crystal; when viewed down the optic axis, the stone reveals a slightly yellowish green core about 5 mm Figure 1. This 11.06-ct almandine-spessartine in diameter surrounded by a darker rim of the same hue. garnet was recently found in Clearwater The most interesting phenomenon, though, is the County, Idaho. Photo 0 Tino Hammid. weak green fluorescence of the emerald when exposed to long-wave ultraviolet radiation (alsovery weakly visible with short-wave U.V radiation]. Microscopy revealed gemological properties of this material suggest that it that the fluorescence was not concentrated in cracks and should be classified as an almandine-spessartine garnet. so could not be related to the presence of oil. Moreover, When the stone was studied with the hand spectroscope, the intensity of the fluorescence clearly correlates with a strong 432.0-nm band that could be attributed to the the intensity of the green coloration. The emission manganese in spessartine was observed, together with spectrum resolved on an AMINCO SPF-500 fluores- absorption characteristics typical of almandine. The cence spectrometer revealed a band at 467 nm and a very refractive index was over the limits (1.81) of the refrac- broad band centered around 510 nm, probably responsi- tometer, and the hydrostatically determined specific ble for the green hue. Further work would be required to gravity was approximately 4.13. Examination with the determine the cause of the emission. microscope revealed a partially healed fracture composed of numerous tiny two-phase fluid inclusions, New source of gem garnets from Idaho. Mr. Leon M. suggesting a possible pegmatitic origin. Agee, of Walla Walla, Washington, recently identified We do not know how much of this garnet is available, and faceted a number of deep brownish red gem-quality but we do know that the area is currently being garnets that had been found by Mr. Kim Boyd in prospected. It is interesting to note that Mr. Boyd found Clearwater County, Idaho. A reader of Gem News, Mr. the garnets while he was placer mining for gold. Agee sent one of the garnets to the editor to examine. Shown in figure 1, the round brilliant-cut garnet mea- Pectolite. Dr. Emmanuel Fritsch also supplied the fol- sures 13.17 x 8.20 mm and weighs 11.06 ct. The lowing information on blue pectolite to Gem News.

Gem News GEMS & GEMOLOGY Fall 1986 187 Pectolitel known under the trade name "Larimar1" is crystals were brought into a dimly lit or darlc room they commonly found at gem shows as attractive greenish would be observed to glow. blue cabochons with flower-like radiating patterns. The crystals were originally purchased (for a rather "Larimarl' is the juxtaposition of "LariI1'the name of the large sum] as natural glow-in-the-darlc quartz crystals. daughter of the mine's developer! Miguel Mendez! and Apparentlx some sort of occult power was attributed to ttmar,llwhich means "sea1' in Spanish (Dan MacAulex them. When the purchaser brought them to Ms. Haas for pers. comm.) in reference to the stone's color. No study she became suspicious and so contacted Gem information on the geologic setting of the mine is News. This is a totally new treatment to us. Unfor- available, However, research is currently being con- tunate]~we were not able to determine how much of ducted on the origin of the color. Work at CIA'S Research this material is being manufactured and sold at the Department demonstrates that the optical absorption present time. spectrum of pectolite is very similar to that of turquoise! with a broad absorption band at about 650 nml in the Undesirable color change in blue zircon, Ms. Janice orangy red. This band is interpreted as being due to the Mack Talcottt of Talcott Enterprises! Inc.! in Olympial copper ion Cu2+ in octahedral coordination. Further Washington! phoned the Gem News editor to aslc if he or evidence of the presence of copper in this gem came from his colleagues had ever heard of color instability in blue a study of the black metallic inclusions in a piece of zircon. One of the company's clients had worn a fine pectolite donated to GIA by Helen Tillet! of St. Thomas! blue zircon ring in a tanning booth for about 20 minutes. U.S. Virgin Islands. X-ray powder diffraction! performed When she emerged, she noticed that the stone had by Chuclc Fryer! identified these inclusions as chalcocite turned a muddy grayish greenish brown! apparently as a Pu2S). result of the exposure to ultraviolet rays. We had never heard of such a change and could find Phosphorescent fake. Ms. Loreen Haas! of Crown Gems no mention of it in the available literature. Therefore! we in Sherman Oalcs! California, was kind enough to send decided to see if we co~~ldduplicate the color change and Gem News three unusual colorless quartz crystals. The also whether the change could be reversed. smallest of these! shown in figure 2) measured 18.1 x Two faceted blue zircons of the same darlc color were 10.1 x 7.3 mml while the largest was recorded at 26.0 x selected, One was exposed to long-wave ultraviolet 14.2 x 12.2 mm. All three of the crystals had been core- radiation for 20 minutes! while the other was kept as a drilled from the base and their centers filled with a color control. The color change was dramatic: from mixture of phosphorescent powder and epoxy resin. The bright blue through a light grayish brown [figure 4) to a bases had then been capped with yellow metal bell caps muddy grayish greenish brown. so that the crystals could be worn 111 an inverted position To reverse the change! we placed the muddy grayish as pendants. Any light source could excite the powder greenish brown zircon on the tip of an upright 80-watt filling to phosphoresce blue-green [figure3),so that if the quartz halogen-powered fiber-optic illuminator. After two hours of exposure to this incandescent light! the stone had completely returned to its original blue color.

Figure 2. This colorless quartz crystal (18.1 x 10.1 x 7.3 mm) was core-drilled Figure 3. After it was exposed to light, and filled with phosphorescent powder the filled quartz crystal show in fig~~re2 and epoxy resin. The piece was then capped glowed blue-green when ploced in o dimly to form a pendant. lit room.

188 Gem News GEMS & GEMOLOGY Fall 1986 Figure 4. The grayish brown zircon on the right was the same color as the blue zircon on the left before it wos exposed to long-wave ultraviolet radiation for 20 minutes. Note the radical color change. The most intense color ob~ainedby this process - o muddy brown - was impossible to photograph because the lights required caused the stone to gradually revert back to its original color. Photo 63 Tino Hammid.

Exposure of the blue zircon to short-wave ultraviolet Direct contact with Sumitomo/s U.S. representative radiation alio produced the same color change from blue provided us with additional information on their prod- to brownl and again the fiber-optic illuminator restored uct. On the basis of the infrared spectra! all of the the original blue color. synthetic diamond pieces are type Ib (dispersed nitro- Mr. Richard Hug of Cincinnati/ Ohio, recently ob- gen]/ which is intrinsically yellow and is often referred served a similar color change in a blue zircon worn in a to in the trade as a "canary" color. This observation of tanning booth. He reported that the zircon regained its diamond type immediately distinguishes the Sumitomo original blue color after it had been placed on top of an diamonds from the vast majority of natural yellow ordinary light bulb for a couple of hours. diamondsl which are type Ia. The synthetic diamonds are primarily being made for two industrial applications: heat sinks in electrical devices (Sumitomots Small, cuttable gem-quality synthetic diamonds: a real- primary market for synthetic single-crystal diamondsj1 ity. In the Spring 1985 Gem News columnl we reported and industrial and surgical tools. The price range is $60 that Sumitomo Electric Industries and the National to $145 per rectangular piece for various sizes up to 0.40 Institute for Research on Inorganic Materials, both in ct. Sumitomo's representative also stated that they Japanl had succeeded in experimentally growing cut- currei~tlymarket the rectangular pieces only for scien- table gem-quality synthetic diamond crystals as large as tific and industrial uses/ and they do not intend to 1 cm and weighing up to 3.5 ct. We have now seen 10 release any of the rough crystals. In additionl the pieces of synthetic diamond that were grown more company is currently experimenting with synthetic recently by Sumitomo and are now being sold for blue diamonds [type IIb] for use as semiconductors/ and industrial applications. These pieces are the property of with synthetic colorless diamonds (type IIa] for indus- Hughes Research Laboratory in Malibu) California/ and trial applications. were brought to the GIA Research Department for Because of the in~plicationsfor the jewelry trade of testing with the department's new infrared spectrome- this new technologyl the CIA Research Department is ter. These fashioned pieces had been sawn, then laser currently documenting the gemological properties of cut, and then partly polished from the original crystals the Sumitomo synthetic diamonds. The Sumitomo (which weighed up to 1.2 ct) into rectangular shapes Company has been very cooperative in providing both weighing up to 0.40 ct and measuring approximately 4 x samples of the synthetic diamonds and technical infor- 4 x 2 min. mation. GIA Research purchased seven pieces of syn-

Gem News GEMS FA GEMOLOGY Fall 1986 189 thetic diamond. Each had two large polished surfaces their fluorescence behavior in that they are inert to long- and various smaller crystal faces around the edges. They wave ultraviolet radiation but fluoresce a greenish yel- ranged from 0.1 1 to 0.37 ct. The largest piece measured low to short-wave ultraviolet radiation. In color, the 3.76 x 3.63 x 1.78 mm. This piece was subsequently Sumitomo synthetic diamonds correspond to a fancy cut for maximum weight retention in an attractive intense yellow. The pieces are often color zoned from faceted stone. The resulting 0.16-ct square-step-cut deep yellow in the center to a narrow zone that is very stone measures approximately 3-48 X 3.33 X 1.73 mm! pale yellow or colorless around the edges. The synthetic with a depth percentage of 5270 and a weight retention diamonds may display prominent internal grain lines of 44Y0. Considering the cost of the original piece of and a ~~cruciformJJstrain pattern when observed between rough ($1451and the assumed cutting cost, the price per crossed polarizers. When the stones are viewed with the carat of this synthetic diamond would be equal to or microscope^ tiny metallic inclusions or white pinpoint exceed the price of a natural diamond of similar hue and inclusions may be observed. In addition! within the clarity. areas of deep yellow color, small colorless "vein-like" On the basis of a preliminary gemological examina- areas are visible. These features in combination are tion! GIA Research has determined that the Sumitomo quite different from those found in natural diamonds of synthetic diamonds have some distinctive properties the same hue. The GIA Research Department is prepar- that aid in their identification. Because they are type Ib) ing a complete report on the Sumitomo synthetic they lack the sharp !!Capef1 lines in the absorption diamonds for publication in Gems t9 Gemology in the spectrum that are characteristic of type la diamonds. near future. For further information! contact Dr. James The Sumitomo synthetic diamonds are also unusual in Shigley, (213)829-2991! extension 305.

Fashion Institute of Technology Miami Beach Convention Center. 581043) Dallas, TX 75258) (2141 presents "20th Century Design! In- Contact: Jewelers International 724-4367. ternational." This symposium will Showcase Inc.! 9835 Sunset Drive, Numerous other shows are held take place in. New York on Satur- Suite 208) Miami, FL 33173; (305) at various hotels and motels in dax November 15! 1986, and will 279-095 1. Tucson (e.g.! the Holiday Inn feature world-renowned authorities Broadway! the Quality Inn, the De- on antique and 20th-century jewe- BIJORHCA will be held January sert Inn) and the Santa Rita) during lry, including: Noelle De Gary, cur- 30-February 3 at the Parc des Ex- this same period. ator of the Muske des Arts Dkco- positions, Vilkpintef Paris. Contact: INHORGENTA 87 will be held Feb- ratifs; Fritz Falk! director of the BIJORHCA)26 Rue de Renard, ruary 13- 17 at the Trade Fair Pforzheim Museum; Peter Hinks, 75004 Paris! France. Telex: 680377 Centre in Munich! West Germany. of Sotheby Parlze Bernet; and BOCIF. Contact: Munchener Messe-und Graham Hughes! past director of The 1987 Tucson Gem and Mineral Ausstellungsgesellschaft mbH, Goldsmiths' Hall. For further infor- Show will be held February 12-15 Messegelande, Postfach 121009, mation! contact the symposium coat the Tucson Community Center. D-8000 Munchen 12! West Ger- ordinator! Jean Appleton! Jewelry The featured species for the show many. Telex: 5212086 AMEG D. Design Resource, (2121 760-7254. this year is quartz. For more information, contact the Tucson Gem International Watch, Clock and Iberjoya will be held January 15-20 and Mineral Society, PO. Box Jewellery Fair will be held February at the Ifema Exhibiton Center in 42543) TucsonJ AZ 85733, 14-17 at the Centrepoint Exhibi- Madrid. Contact: Instituci6n Ferial Also in Tucson, February 7-12) tion! Centre Sydney. Contact: World de Madrid! Avenida de Portugal s/n, the American Gem Trade Associa- Trade Promotions Pty. Ltd., 144 2801 1 Madrid! Spain. Telex: 44025 tion (AGTA]show will be held at Riley Street, East Sydney, New IFEMA E. the Doubletree Hotel. During that South Wales, Australia. Telex: AA 176428 FSASYD. Vicenzaoro 1 will be held January time, the winners of the Spectrum 15-22 at the Trade Fair Pavillions in Award [a jewelry design contest Platinum Jewellexy Fair 87 will be Vicenza. Contact: Ente Fiera de specifically aimed at the effective held February 16- 17 at the Imperial Vicema! Viale degli Scaligeri 34) use of colored stones) will be an- Hotel! Tokyo, and on February 20 at 36100 Vicenza) Italy. Telex: 48 1542 nounced. The deadline for entries the Hilton Hotel in Osaka. Contact: FIER VII. is November 4! 1986. For more in- Platinum Guild International K.K., formation about the contest) con- Imperial Tower 13A) 1- 1-1 Uchisai- Jewelers International Showcase tact the AGTA headquarters at the wai-tho) Chiyoda-lzu)Tokyo 100) will be held January 17- 19 at the World Trade Center #I8 1, PO. Box Japan. Telex: 129817 PGIKKJ.

190 Gem News GEMS & GEMOLOGY Fall 1986