Gems&Gemology VOLUME XXII SUMMER 1986 ~e quarterly journal of the Gemological Institute of America SUMMER 1986 Volume 22 Number 2 Gems&Gemology TABLE OF CONTENTS FEATURE The Coscuez Mine: A Major Source of Colombian Emeralds ARTICLES Ron Ringsmd The Elahera Gem Field in Central Sri Lanka Mahinda Gunawardene and Mahinda S. Rupasinghe NOTES Some Unusual Sillimanite Cat's-Eyes AND NEW ' E. Giibelin, M. Weibel, and C. R. Woensdregt TECHNIQUES An Examination of Four Important Gems C. W. Fryer and John I. Koivula Green Glass Made of Mount Saint Helens Ash? Kurt Nassau REGULAR Editorial Forum FEATURES Gem Trade Lab Notes Gem News Gemological Abstracts Book Reviews Suggestions for Authors ABOUT THE COVER: Currently one of the most productive, if little known, emerald mines in Colombia is the Coscuez mine. The 14.52-ct emeraldillustrated here shows the highly saturated bluish green color that is characteristic of emeralds from this locality, which lies only 10 kmfrom the famous Muzo mine. Ron Ringsrud's articlein this issue takes a comprehensivelook at Coscuez, its history, geology, mining activities, and the emeralds found there. Photo C 1986 Harold el Erica Van Pelt-Photographers, Los Angeles, CA. 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. @I986 Gemological Institute of America All rights reserved ISSN 001 6-626X SUMMER 1986 Volume 22 Number 2 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 Technical Editor Sally A. Thomas Jeffrey M. Burbank 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 Robert Crowningshield Anthony R. Kampf Kurt Nassau REVIEW BOARD New York, NY Los Angeles, CA BernaidsviIIe, Nf Pete Dunn Robert E. Kane Glenn Nord Washington, DC Los Angeles, CA Los Angeles, CA Dennis Foltz John Koivula Ray Page Santa Monica, CA Santa Monica, CA Santa Monica, CA Chuck Fryer Henry 0. A. Meyer George Rossman Santa Monica, CA West LaFayette, Indiana Pasadena, CA C. S. Hurlbut, Jr. Sallie Morton James E. Shigley Cambridge, MA San lose, CA Sunta Monica, CA SUBSCRIPTIONS Subscriptions in the U.S.A. are priced as follows: $29.50 for one year (4 issues), $82.50 for three years 112 issues). Subscriptions sent elsewhere are $40.00for one year, $1 15.00 for thrcc years. 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THE COSCUEZ MINE: A MAJOR SOURCE OF COLOMBIAN EMERALDS By Ron Ringsrud The Muzo emerald district, in Boyacd, henever fine emeralds are discussed in the gem Colombia, contains several mines. w trade, the term Muzo is invariably used to describe Although the Muzo mine is undoubtedly the best. Yet Colombia's Muzo district actually the best known, the Coscuezmineis rapidly encompasses several mines, of which two are currently gaining significance as a major source of major producers: Muzo and Coscuez. Many stones prop- fine emeralds. Yet few in the trade outside erly referred to as "Mum emeralds" actually come from of Colombia are aware of the importance of Coscuez (figure I), which lies only 10 km from the Muzo Coscuez orJznow about the emeralds mined 2). there. The '~oscuezmine is literally mine (figure Although smaller than Muzo, the Coscuez hundreds of years old, and its history is mine has for more than 300 years produced some of the closely tied to that of Muzo, Located only best emeralds from the Muzo region, at times in quantities about 10 lzm apart, the two areas also share that have even surpassed the Muzo mine. many geologic features and both are Five years ago, Gems o) Gemology published an article currently exploited using open-cut mining outlining the history, geology, and production of Colom- methods. The Cosczzez emeralds are similar bia's two major emerald-mining regions: Muzo and Chivor to Muzo stones in their physical properties, (Keller, 198 1). Soon after that article appeared, however, but they occurin a somewhat broaderrange production from the Chivor region began to fall, while that of hue and saturation. Prospects for even from the Coscuez mine accelerated rapidly. During this greaterproduction at Coscuez in the future same period, the Muzo mine continued to supply good are good. quantities of emeralds. Today, most of the emeralds mined in Colombia come from the Muzo district, and the Cos- cuez mine has grown to become the second largest pro- ducer of emeralds in Colombia. Yet in spite of its prominence, little has been written ABOUT THE AUTHOR specifically on Coscuez or the Coscuez emeralds in the Mr. Ringsrud is a major partner in Constellation jewelry and gemology literature, and few in the trade out- Gems, Inc., an import firm specializing in Colombian emeralds, which is headquartered in side of Colombia are aware of its importance as a major Los Angeles, California. source of fine emeralds. In March 1984, the author traveled Acknowledgments: The author would like to thank to Coscuez in the company of local dealers; two years later, the following people for their assistance in in May 1986, he revisited the mine as a guest of Colombian researching and completing this article: Samuel, Mines Co., a major stockholder of ESMERACOL, the pres- Amnon, and Albert Gad; Jack and James Rotlewicz; Jorge Rozo; Eileen Weatherby; Gabriel Acufia; Dr. ent leaseholder of the Coscuez mine. Based on information Alfonso Soto: Raul Escobar; Humberto Rodriguez; gathered during these visits as well as from other sources, Guillermo Cano; Dr. Peter Keller; Dr. James Shigley; this article reviews the fascinating history of mining at Benny Bazalel: Alberto Florez; and Cornelio Torres. Unless otherwise noted, allof the locality photos are Coscuez, describes thegeology of the area and the nature of by the author. mining operations, and examines the gemology of the Cos- 0 7986 Gemological Institute of America cuez emeralds. Emeralds from Coscuez GEMS & GEMOLOGY Summer 1986 67 HISTORY jungle traps, camouflaged pits, and numerous for- Much interesting history about the Spanish dis- tifications. covery and conquest of the emerald regions of Col- The Muzos inherited from their ancestors the ombia was published in 1948 by the Bank of the ancient legends surrounding the Fura-Tena, a co- Republic after it took over the administration of lossal pair of granite peaks (the tallest is 625 m emerald mining from the government. The author above the Minero River), approximately 40 km was G. Otero Mufioz, head of the Colombian Insti- from the Coscuez mine. As one approaches from tute of History. Unlike many other publications, the east, the Fura-Tena looms up majestically as a Esmeraldas de Colombia provided considerable sentinel to all who enter the emerald region. One information specifically on Coscuez. Much of Muzo legend states that Fura is the prince and what follows is from this source. Tena is the princess, both born to the god of the In their conquest of South America, beginning mountains. The god gave them wealth in the form in the 16th century, the Spaniards encountered of rich veins of emeralds, one of which was sacred Colombian emeralds among the local Indians as and not to be touched. A devil named Zarv con- far north as Mexico and as far south as Peru and vinced the princess to take the forbidden stones. northern Chile (Sinkankas, 1981). Judging from As she and the prince attempted to remove the the emeralds found in these ancient Indian sites, cursed emeralds, the god turned them into the two archaeologists believe that pre-Colombian tribes granite peaks, and their tears of remorse became began to systematically mine and trade emeralds the Minero River.