VOLUME xxvH 1 GEMS&GEMOLOGYWINTER 1991 1 TABL Buyer Beware! Alice S. Keller Marine Mining of Diamonds Off the West Coast of Southern Africa John 1. Gurney, Alfred A. Levinson, and H. Stuart Smith Sunstone Labradorite from the Ponderosa Mine, Oregon Christopher L. Johnston, Mickey E. Gunter, and Charles R. Knowles NOTESAND NEWTECHNIQUES Curves and Optics in Nontraditional Gemstone Cutting Ar~hzzrLee Anderson An Examination of Nontransparent "CZ" from Russia Robert C. Kammerling, John I. IZoivzzla, Robert E. IZane, Emmanuel Fritsch, Sam Mzzhlineister, and Shane F,McClure Gem Trade Lab Notes Gem News Book Reviews Gemological Abstracts Annual Index ABOUT THE COVER: Potentially enorn~ousquantities of fine diamonds have been identified off the western coast of southern Africa. The lead article in this issue examines the probable sources of these diamonds and some of the unusual methods being used to recover them from the sea. The AmFAR Diamond Mask shown here is composed of 936 fine diamonds, weighing a total of 135.9 cl, set in 1SK gold and platinum. The largest stone is 3.00 ct. The gold was donated by the World Cold Council and the platinum by Platinum Guild International; the diamonds were provided by the William Goldberg Diamond Corp. Design and fabrication are by Henry Dunay. The mask will be auctioned at Christie's New York on April 14, 1992. The proceeds will go to the American Foundation For AIDS Research (AmFAR). Photo 0 Harold e) Erica Van Pelt-Photographers, Los Angeles, CA Typesetting for Gems &> Gemology is by Graphix Express, Santa Monica, CA. Color separations are by Effective Graphics, Compton, CA. Printing is by Waverly Press, Easton, MD. 0 1992 Gemological Institute of America All rights reserved SSN 0016-626X EDITORIAL Editor-in-Chief Editor Editor, Gem Trade Lab Notes STAFF Richard T Licldicoat Alice S. Keller C, W Fryer 1660 Stewart St. Associate Editors Santa Monica, CA 90404 Editor, Gemological Abstracts William E. Boyajian Telephone: (800) 42 1-7250 x25 1 Dona M. Dirlam D. Vincent Manson John Sinlzankas Subscriptions Editors, Book Reviews Gail Young Elise B. Misiorowslzi Technical Editor Telephone: (800) 421-7250, x201 Loretta B. Loeb Carol M. Stockton FAX: (3101 453-4478 Editors, Gem News Assistant Editor Contributing Editor John 1. '~oivula Nancy K. Hays John I. Koivula Robert C. Kammerling PRODUCTION Art Director Production Artist Word Processor STAFF Lisa Joko Carol Silver Ruth Patchick EDITORIAL Robert Crowningshield Robert C. Kammerling Kurt Nassau REVIEW BOARD New York, NY Santa Monica, CA PO. Lebanon, N/ Alan T. Collins Anthony R. Kampf Ray Page London, United Kingdom Los Angeles, CA Santa Monica, CA Dennis Foltz Robert E. Kane George Rossman Santa Monica, CA Santa Monica. CA Pasadena, CA Emmanuel Fritsch John 1. Koiviila Kenneth Scarratt Santa Monica, CA Santa Monica, CA London, United Kingdom C. W Fryer Henry 0. A. Meyer Karl Schmetzer Santa Monica, CA West Lafayette, IN Petershausen, Germany C. S. Hurlbut, Jr. Sallie Morton Cambridge, MA Son lose, CA SUBSCRIPTIONS Subscriptions in the U.S.A. are priced as follows: $49.95 for one year (4 issues), S119.95 for three years (12 issues). Subscriptions sent elsewhere are $59.00 for one year, $149.00 for three years. Special annual subscription rates are available for all students actively involved in a GIA program. $39.95 U.S.A., $49.00 elsewhere. Your student number must be listed at the time your subscription is entered. Single issues may be purchased for $12.50 in the U.S.A., $16.00 elsewhere. Discounts are given for bulk orders of 10 or more of any one issue. A limited number of back issues of G&G are also available for purchase. Please address all inquiries regarding subscriptions and the purchase of single copies or back issues to the Sub- scriptions Department. To obtain a Japanese translation of Gems d Gemology, contact the Association of Japan Gem Trust, Okachimachi Cy Bldg, 5-15-14 Ueno, Taito-ku, Tokyo 110, Japan. MANUSCRIPT Gems ed Gemology welcomes the submission of articles on all aspects of the field. Please see the Suggestions for Au- SUBMISSIONS thors in this issue of the journal, or contact the editor for a copy. Letters on articles published in Gems a) Gemology and other relevant matters are also wclcome. COPYRIGHT Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. AND REPRINT copyright law for private use of patrons. Instructors are permitted to photocopy isolated articles for noncommercial PERMISSIONS classroon~use without fee. Copying of the photographs by any means other than traditional photocopying techniques (Xerox, etc.1 is prohibited without the express permission of the photographer (where listed) or author of the article in which the photo appears (where no photographer is listed]. For other copying, reprint, or republication pern~ission, please contact the editor. Gems a) Gemology is published quarterly by the Gemological Institute of America, a nonprofit educational organization for the jewelry industry, 1660 Stewart St., Santa Monica, CA 90404. Postmaster: Return undeliverable copies of Gems a> Gemology to 1660 Stewart St., Santa Monica, CA 90404. Any opinions expressed in signed articles are understood to be the views of the authors and not of the publishers. hat might atfir$t!glancs.4ppt$i.r td hea small 'ifem in:theGem w News 'columnof this issue raise^ a very important concern for thegemological community. An experienced colored-$tone dealer traveled to Vietnam to obtain someof the new, often ~pectacular rubies that have recently emerged from this third-world nation (and were described in depth in the Fall 1991 issue of Gems o> Gemology). He purchased a significant parcel of rough stones, the largest of which was 22 ct, The color and clarity of the material appeared to be superb, although it was difficult to view theinterior of the atones because of their "tumbled" exterior and the bits of dirt and matrix that clung to small pits. When the largest stone was ~reformed,it became obvious that some- thingwag wrong. The dealerimrnodiatcly sent tiix of the stones, including the preformed piwe, to the CIA Gem mde,&gbordtory for  * bIdentific.atiiin;Examin! tiuli with a microscope readily revealed that 1.' :: ' one of thepieceg of rough (the.km$tllest one) was a natural ruby-and that thepreform contiinidthe gas bubble5:andcurv&ditrtaetypiul È of a flame-fusionsynthetic. Examination ,Of theother pieces was diifi- cult,:again because of the rough nature of theexterior but faint curved striae were..determiniidin two of thestones with magnifica- tion. The fact that all but one of the pieces of "rough" submitted were flame-futlonsynthetics wasconfirmed by infrared @ect~osco~~.. One can only,speculate on the loss in dollars, but it laundoubtedly $tibatinti& The ~wner~agreidtoshare this experience! with our read- ers to.reinforce a rne~~~g6that weÑn. Gems Gemology, GIA, and the GIA Cem tide ~abon>t~ry-+havebeen piomtitifig lot decades. Study, examine, le~rn,,K~~W~~ore..y~ubuy.Whilein most cases, when you buy from a legi tima tiisupplier,. the supplier will "makt . goodMifthestone is lateifound.t@hi ireinedGia$ynth~qLho:.8~<~ guarantees holdat many of the localities tha tare producing thefinest stone?... today.Andno. locality la too isolated to impittthes,9nthetic. counterpart!) of their valued'gemiksources. '¥.? -'.I w, , j--,. ",jg . Alicegaitor S ;Kellcr . , Editorial , GEMS 81 GEMOLOGY Winter 1991 By John J. Gurney, Alfred A. Levinson, and 11. Stuart Smith A vast resource of gem-qnality diamonds exists off the west coast of southern @ecausethe continued diamonds supply are the of heartfine ofdiamonds the jewelry from trade, the Africa. Over the course of millions of , - mines into the marketplace is of critical importance to years, many diamond-bearing kimberlite this industry. According to the Central selling Organi- pipes in the Orange River drainage basin sation, about one-eighth (approximately 13 million have been extensively eroded and the carats) of the diamonds now mined annually eventually released diamonds transported to the west coast. Raised marine deposits now end up in jewelry (figure 1). Yet for the largest producer on land have yielded almost 100 million of diamonds in 1990, the Argyle mine in Western carats of predominantly gem diamonds; Australia (36 million carats), fine gem-quality diamonds similar marine deposits and feeder represented only about 5% of the total yield. In addition, channels are now known to exist off- older deposits of gem-quality diamonds are gradually shore. Techniques for exploiting the off- being exhausted. For example, the total production at the shore resources have been proved on a Kimberley pool of mines was 1,173,042 ct in 1980 but small scale in shallow (<I5m) waters. only 574,188 ct in 1990 (De Beers Consolidated Mines New technological developments in Ltd., 1981, 1991). underwater mining systems have In the future, the steady supply of gem diamonds to progressed to the point where mining has the jewelry industry will depend on the discovery of commenced in deep (about 100 m) Namibian waters. It is anticipated that new deposits and the engineering expertise to extract production of diamonds from the sea will I the diamonds economically. Because the search for new increase substantially in the future. diamond reserves in conventional primary (e.g., lzimber- I lite or lamproite) or secondary (e.g., alluvial) deposits is very expensive and generally has a low probability of success, mining concerns are looking to the extraction of diamonds from known, if unconventional, sources, such as the undersea deposits off the west coasts of ABOUT THEAUTHORS South Africa and Namibia. Or. Gumey a prtifeSSW in tAe Dopartniwit of These exceptional deposits of gem-quality diamonds Gsocftemsfry, Universityof c47e Town, flOrtdabOSCh, Soufft Africa.