Winter 1982 Gems & Gemology

WINTER 1982 Volume 18 Number 4 TABLE OF CONTENTS EDITORIAL 185 In Tribute to Robert M. Shipley, Jr. FEATURE 186 The Chanthaburi-Trat Gem Field, Thailand ARTICLES Peter C. Keller 197 Gemstones with Alexandrite Effect E. Giibelin and K. Schmetzer 204 Gem-Quality Grossular Garnets D. Vincent Manson and Carol M. Stockton NOTES 214 Artistryfin Rock Crystal: The Van Pelt Collection AND NEW John Sinkankcis TECHNIQUES 221 Gem-Quality Friedelite from the Kalahari Manganese Field near Kuruman, South Africa Herbert S. Pienaar Tourmaline as an Inclusion in Zambian Emeralds John I. Koivula REGULAR Gem Trade Lab Notes FEATURES Editorial Forum Gemological Abstracts Book Reviews Gem News Index to Volume 18, Numbers 1-4 ABOUT THE COVER: This unusual quartz egg, measuring 3 in. x 5 in. (7.6 cm x 12.7 cm) is covered with 416 triangular facets and has been hollowed out so that the walls are only 3 mm thick. The techniques used by Harold and Erica Van Pelt to fashion this unusual art object are described by Dr. John Sinkankas in this issue. The egg is resting on a 363-ct aquamarine pedestal, and the quartz base sits on four 5-ct aquamarine cabochons. Photograph 1982 Harold and Erica Van Pelt, Los Angeles, CA. Composition for Gems & Gemology is by Printed Page Graphics, Fullerton, CA. The color separations are done by Effective Graphics, Compton, CA. Printing is by Waverly Press, Easton, MD. "1983 Gemological Institute of America. All rights reserved. ISSN 001 6-626X EDITORIAL Editor-in-Chief Managing Editor Editor, Gem Trade Lab Notes STAFF Richard T. Liddicoat, Jr. Alice S. Keller Chuck Fryer Associate Editor 1660 Stewart St. Santa Monica, CA 90404 Editor, Gemological Abstracts Peter C. Keller Dona M. Dirlarn Telephone: (2131 829-299 1 Associate Editor Subscriptions Manager Editor, Book Reviews D. Vincent Manson Janet M. Fryer Michael Ross Contributing Editor Editorial Assistant Editor, Gem News John I. Koivula Sally A. Thomas Stephanie Dillion PRODUCTION Art Director Cover Design GIA Photographers STAFF Susan Kingsbury Peter johnston Mike Havstad Tino Hammid EDITORIAL Robert Crowningshield C. S. Hurlbut, Jr. Kurt Nassau REVIEW BOARD New York, NY Cambridge, MA Bernardsville, N/ Pete Dunn Anthony R, Kampf Glenn Nord Washington, DC Los Angeles, CA Los Angeles, CA Dennis Foltz Robert E. Kane George Rossrnan Santa Monica, CA Los Angeles, CA Pasadena, CA Chuck Fryer John Koivula John Sinkankas Santa Monica, CA Santa Monica, CA San Diego, CA Sallie Morton San lose, CA SUBSCRIPTIONS Subscriptions in the U.S.A. are priced as follows: $22.50 for one year (4 issues), $60.00 for three years (12 issues). Subscriptions sent elsewhere are: $32.00 for one year, $85.00 for three years. Special annual subscription rates are available for all students actively involved in a GIA program: $17.50 U.S.A., $27.00 elsewhere. Your student number must be listed at the time your subscription is entered. Single issues may be purchased for $6.00 in the U.S.A., $8.00 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 Subscriptions Manager. MANUSCRIPT Gems a) Gemology welcomes the submission of articles on all aspects of the field. Please see the Suggestions for SUBMISSIONS Authors for preparing manuscripts in the Summer 1981 issue of the journal or contact the Managing Editor for a copy. Letters on articles published in Gems a) 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 Managing PERMISSIONS 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. Any opinions expressed in signed articles are understood to be the views of the authors and not of the publishers IN TRIBUTE TO ROBERT M. SHIPLEY, JR. obert M. Shipley, Jr., the elder son of the founder of the Gemological Institute R of America, passed away on September 10 after a long illness. He was 69 years old. Bob Jr., as he was known to many of his friends in the gemological field, was a great asset to his father in the early days of GIA. He came west from Wichita to join his father in 1933, and his expertise in the laboratory field and in the devel- opment of instrumentation for gemologists quickly became apparent. The younger Shipley soon became Director of the GIA Laboratory and was instrumental in es- tablishing its reputation across the nation. In many respects, Robert Shipley, Jr., was a genius in instrumentation. Prior to his efforts, gemologists were largely dependent on instrumentation from the mineral- , 'ogical field. Shipley decided that dark-field illumination would be of great benefit . for examining the interior of gemstones and that low-power stereoscopic magnification would be a boon to the gemologist. In 1937, he applied for a patent on the combination of binocular magnification with dark-field illumination for the ex- amination of gemstones; 'the patent was granted in 1938. The stoneholder that he developed for that early Diamondscope is still in use today, almost unchanged from the original design. When Edwin Land developed Polaroid, Shipley immediately saw the advantages over the expensive and small Nicol prisms and made, with Raoul Francouer, a French tool and dye maker, the first gem polariscope. Other instruments Shipley developed include the original optical colorimeter, an electronic colorimeter, a uni- versal motion immersion stage, a vertical equivalent of the endoscope for testing drilled pearls, an analyzing refractometer, a pocket refractometer, and a gemological polarizing microscope. Shipley also assisted his father in the preparation of GIA1s Home Study courses, particularly the course on advanced gemology. He taught many classes and acted for a number of years as Director of Education as well as Research. An officer in the Air Force reserve, Shipley was called to active duty in 1941. He served in the U.S. and England during World War I1 and was given a medical dis- charge in 1944. After World War 11, he founded an instrument manufacturing com- pany, which was sold to GIA around 1951. He then moved to Cloverdale, California, north of San Francisco, where he continued his inventive ways with a research laboratory. He developed tree shakers for the fruit industry of northern California and also equipment to pick up the fruit after it had fallen. He subsequently sold the research laboratory to a large midwestern manufacturing firm. Robert Shipley, Jr., is survived by his wife Mary and two sons. Editorial GEMS & GEMOLOGY Winter 1982 185 THE CHANTHABURI-TRAT GEM FIELD, THAILAND By Peter C. Keller With th e recent drastic decline in hailand has been a world supplier of gem ruby and production from the classic ruby m ine s of T sapphire since the latter part of the 19th century, Burma, Thailand has become the wo rld's although the deposits were not thought to be as impor major source of gem ruby. The majority tant as those of neighboring Burma. In 1963, however, the of the ruby produ ction, as well as som e Burmese deposits were nationalized, and supplies of fine significant sapphire produ ction, comes gems from these mines declined rapidly. The fact that so from the provin ces of Chan tliabuti and little is produced in Burma today has catapulted the Thai Ttat in southeastern Thailand. Thi s article reviews the geology of th ese deposits into importance. An estimated 70% of the world's alluvial deposits and describes the wide high-quality gem rubies come from Thailand. Of these, range of methods used to mine th e 85% to 90% come from the Chanthaburi-Trat district corundum. Gemologically, the Thai alone (Aranyakanon and Vichit, 1979). While the overall rubies are distinguished by their violet quality of these rubies is not as high as those found in overtone, inhibited fluor escence, and Burma, exceptional stones are seen (figure 1). characteristic inclusion s. Also discussed The gem deposits of the Chanthaburi-Trat (formerly is the heat treatment of corundum to Krat] area are entirely alluvial, having eroded out of deeply enhance color, which has become a major weathered basalt flows . The region can, however, be di industry in Clianthaburi.The newest vided into two mining districts based on the type of co product, "golden" sapphire, is examined, rundum produced. The first lies to th e west, near the including the apparent stability of the color produced and clues to the det ection town of Chanthaburi (figure 2) and in the Chanthaburi of the heat treatment. Province. It includes th e famous Khao ploi Waen and Bang Kha Cha mining areas, known for their production of blue, blue-green, and yellow sapphires as well as black ABOUT THE AUTHOR star sapphires. The second district, approximately 45 krn Dr. Keller is director of educa tion at the to the east of Chanthaburi, in Trat Province, is the cur Gemological Institute of America,Santa Monica, California. rently very active Bo RailBo Waen mining area known for its significant production of ruby. In fact , Bo Rai/Bo Waen, Acknowledgments: The author wishes to thank the many people who con tributed to together with the Pailin area 27 km to the northeast in this article in a variety of ways.

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