Winter 1999 Gems & Gemology

WINTER 1999 VOLUME 35 NO. 4 TABLE OF CONTENTS EDITORIAL 173 Gems & Gemology Turns 65 Richard T. Liddicoat and Alice S. Keller 174 LETTERS FEATURE ARTICLE 176 Classifying Emerald Clarity Enhancement at the GIA Gem Trade Laboratory Shane F. McClure, Thomas M. Moses, Maha Tannous, pg. 185 and John I. Koivula NOTES AND NEW TECHNIQUES 186 Clues to the Process Used by General Electric to Enhance the GE POL Diamonds Karl Schmetzer 192 Diopside Needles as Inclusions in Demantoid Garnet from Russia: A Raman Microspectrometric Study Michael S. Krzemnicki pg. 187 196 Garnets from Madagascar with a Color Change of Blue-Green to Purple Karl Schmetzer and Heinz-Jürgen Bernhardt REGULAR FEATURES 202 Gem Trade Lab Notes 208 Gem News 224 Book Reviews 226 Gemological Abstracts 235 Index pg. 193 ABOUT THE COVER: In response to concerns expressed by the trade over the degree of pg. 201 clarity enhancement in emeralds, GIA Gem Trade Laboratory researchers have devised a methodology to establish the size, number, and position of filled fissures in an emerald, in order to classify the apparent degree of clarity enhancement achieved. The lead article in this issue reports on this research and the resulting classification system. The 10.5 ct emerald crystal in this gold and platinum pendant is from Jos, Nigeria. The pendant was designed by Elena Villa, and manufactured by Hans Dieter Krieger; it is courtesy of Gebrüder Bank, Idar-Oberstein, Germany. Photo © Harold & Erica Van Pelt––Photographers, Los Angeles, California. Color separations for Gems & Gemology are by Pacific Color, Carlsbad, California. Printing is by Fry Communications, Inc., Mechanicsburg, Pennsylvania. © 1999 Gemological Institute of America All rights reserved. ISSN 0016-626X was in 1934 that Robert M. Shipley, founder of both GIA and the American Gem Society, pub- lished the first issue of Gems & Gemology. The journal began as a bi-monthly, pamphlet-sized publication with three holes punched for convenient storage in a loose-leaf binder. I wish Robert Shipley could be with us now to see the full-color, 180 page, Fall 1999 Symposium Proceedings issue 65 years after his brainchild first appeared. I believe (and our authors tell me) that G&G is the most rigorously peer-reviewed publication in gemology and allied sciences alike. We felt that such a review process was critical if gemology was to achieve the status as a science that gems and jewelry had achieved as an industry. We also rec- ognize that, unlike the situation with most scientific journals, our readers encompass a broad range of education and experience. Through careful editing, we work to make every item as useful to the advanced researcher as it is to the new G.G. or the gemologist with 20 years of experience. Over time, some articles have been portentous, others pretentious. I recall, for instance, a piece that Shipley and I wrote in 1941, which we titled “A Solution to Diamond Color Grading Problems.” Obviously, diamond color grading problems remain to this day. Nevertheless, each article has contributed something to the body of knowledge in gemology. Looking back, it’s been an exciting, exhilarating journey. I am proud to have been part of such a dynamic evolution, and I look to the future of gemology, and Gems & Gemology, with anticipa- tion and great expectations. Richard T. Liddicoat Editor-in-Chief where will the next 65 years take us? What once seemed fantastic—a computer that fits in the palm of your hand—now seems ordinary. What once seemed impossible—the nondestructive identification of non-surface-reaching inclusions—is becoming routine. What will change in gemology over the next several decades? Let us look to the current issue for some clues. The lead article, on emerald clarity-enhancement classification, is in response to concerns regarding the many new fillers being used to enhance emeralds. The future will see more fillers and even more-sophisticated treatments in other gem materials. The methods developed by General Electric to treat diamonds—as discusssed in Karl Schmetzer’s article on possible GE POL-related patents, and updated in the Lab Notes item on the new GE-processed yellow-green diamonds—are just two examples of the resources now being devoted to enhancement and synthesis. At the same time, gemology is becoming increasingly sensitive to world affairs. The lead Gem News entry and a special section of Gemological Abstracts address the challenges of making a country-of-origin determination for Angolan diamonds. This is in response to demands by U.S. politicians that diamonds be “identified” in an attempt to bar from the market stones that are being sold to support the atrocities committed by Angolan rebels. We at Gems & Gemology will continue to work with researchers worldwide to address critical issues. Although good research takes time, we will make every effort to disseminate reliable infor- mation as quickly as possible. We plan to use our Web site (www.giaonline.gia.edu) to give regular updates on developments in gemological research, and eventually to provide real-time reports from new and important gem localities. As computing and publishing technologies coalesce to provide consistent color reproduction on screen, our vision of the future shows a fully digitized version of the journal itself. We have a great foundation, provided by giants such as Robert M. Shipley and Richard T. Liddicoat. With our current combination of dedicated researchers and expert reviewers, we have a future as exciting and exhilarating as the past that propels us forward. Alice S. Keller Editor Editorial GEMS & GEMOLOGY Winter 1999 173 Comments on “Identification of first examined them in Carlsbad. Perhaps this mate- Emerald Filling Substances” rial, in its pure state, was sensitive to the tempera- ture and pressure changes involved in shipping to First, let me congratulate the authors of the the United States. As a result of this letter, I asked Gems & Gemology [Summer 1999] article on emer- an experienced color grader to re-examine the sam- ald filling substances. Second, I would like to raise ples, and he thought the color should be described the following points: as a “desaturated, very light yellow-green.” There is so little color in the material that I would not 1. The language in Box B on page 88 is potentially expect it to affect the color of an emerald. confusing. Antonio Negueruela is mentioned Although we accept the statement that Mr. fourth on the list of cedarwood oil distributors Negueruela’s cedarwood oil is 100% natural, our who replied to the authors’ inquiries, and some point was that spectroscopic techniques cannot dis- sentences later it is reported that “Three distrib- tinguish an all-natural cedarwood oil from one that utors stated that the material was all natural, contains synthetic ingredients. For this reason, we but the fourth acknowledged a considerable advise against assuming that any emerald clarity- amount . of synthetic ingredients.” Several enhanced with cedarwood oil has been treated only people who have read the article believe that we with natural materials. The “presumed natural” are the ones using these ingredients. filler categories were intended both as a contrast to 2. Our answer to the authors’ inquiry on January 25, “artificial resins” (which cannot be natural) and as a 1999, was that our oil was 100% natural. In sub- reminder that GIA has no technique that proves sequent correspondence, we included a detailed that a filling substance is natural. list of the all-natural ingredients in our cedar- Mary Johnson, Ph.D. wood oil. GIA Gem Trade Laboratory 3. In none of our laboratory’s tests did we detect any Carlsbad, California greenish coloring to our cedarwood oil. (It is a colorless to pale yellow viscous liquid just after it has been purified.) Lab Notes to the Rescue Once again, Gems & Gemology has come to the In no case is our oil “presumed natural oil,” but rescue. While reading through the Lab Notes sec- rather it is “genuine natural oil.” tion of the Spring 1999 issue, I noted the reference Antonio Negueruela to “Imitation Tahitian Pearls.” Antonio Negueruela S.A. At the time, I was taking a brief break from an Madrid, Spain appraisal I was doing on items seized by Canada Customs. One of the items I had just opened was an envelope containing a pair of black “pearl” earstuds. In Reply Imagine my surprise to find that these two 12 mm We did not mean to imply that Mr. Negueruela’s beads were identical in all respects to those you had company uses synthetic ingredients; only that one described in the Lab Note! of the four companies that responded had indicated By the way, the origin of the seizure was New that such ingredients were incorporated into its York, but that does not pin down where these items product. We regret the resulting confusion, as Mr. are being manufactured. Negueruela had indeed told us that his company’s Thanks for the guidance. cedarwood oil was all-natural. Anne Neumann On the matter of coloring, both samples we Harold Weinstein Gemmological Laboratory received were translucent and semi-solid when we Toronto, Ontario, Canada 174 Letters GEMS & GEMOLOGY Winter 1999 Reflectivity Reading of aluminum oxide has been recommended by Dr. K. Synthetic Moissanite Nassau and H. Schonhorn (1977–1978). It certainly is adequate for removing about 50 atomic layers of In the Letters section of the Summer 1999 issue (pp. SiO2 from synthetic moissanite, which has a hard- 80–81), Dr. Mark Kellam of C3 described how the ness of 9.5. reflectivity reading of synthetic moissanite can be Another approach is to use the water drop test lowered by converting the outermost layers of SiC (Hanneman, 1978b).

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