Abduriyim, Ahmadjan and McClure, Shane F. and Rossman, George R. and Leelawatanasuk, Thanong and Hughes, Richard W. and Laurs, Brendan M. and Lu, Ren and Isatelle, Flavie and Scarratt, Kenneth and Dubinsky, Emily V. and Douthit, Troy R. and Emmett, John L. (2011) Research on Gem Feldspar from the Shigatse Region of Tibet. Gems and Gemology, 47 (2). pp. 167-180. ISSN 0016-626X http://resolver.caltech.edu/CaltechAUTHORS:20110909-144724886
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The existence of a natural red andesine deposit in China/Tibet has been the subject of controversy since 2006. In late September 2010, an international group traveled to the Shigatse region of Tibet and visited two reported andesine occurrences, at Zha Lin village and the Yu Lin Gu alluvial fan. These sites are located ~3 km from the previously investigated Bainang andesine mining area near Nai Sa village. The Zha Lin deposit appeared genuine, but the group could not confirm the authenticity of the Yu Lin Gu occurrence, and no primary andesine-bearing source rocks were found in either area. Some of the samples had glassy surface residues that are difficult to explain naturally, while initial argon isotopic measurements of a few Zha Lin and Yu Lin Gu andesines (without glassy residues) showed that they had not been heated. Laboratory studies of the Tibetan samples—and a comparison to known-treated red andesine from Inner Mongolia—showed that it may be possible to separate these feldspars using a combination of several advanced destructive techniques, but this methodology is not practical for gem testing laboratories. More detailed investigations will be needed to establish feasible identification criteria for natural-color andesine from Tibet.
|Additional Information:||© 2011 Gemological Institute of America. Summer 2011. The authors are grateful to Christina Iu (M.P. Gem Corp., Kofu, Japan) for supporting and organizing the field trip, and to miner Li Tong and his wife Lou Li Ping (Tibet Andesine, Shenzhen, China) for allowing access and guiding us to the localities. Marco Cheung (Litto Gems, Hong Kong) is thanked for arranging a donation of two parcels of Inner Mongolian andesine that were reportedly treated in China. Special thanks to the ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Macquarie University, Sydney, Australia, for LAICP-MS chemical analyses; to Ross Pogson of the Australian Museum, Sydney, for powder X-ray diffraction analysis; and to Terry Coldham, president of the Gemmological Association of Australia, Sydney, for his cooperation with the copper diffusion heating experiments. Ken Farley at Caltech assisted with the argon isotope measurements. Thanks also to Kousuke Kosuda of the National Institute for Materials Science (NIMS), Tsukuba, Japan, for his help with electron microprobe analyses.|
|Official Citation:||Research on Gem Feldspar from the Shigatse Region of Tibet Ahmadjan Abduriyim, Shane F. McClure, George R. Rossman, Thanong Leelawatanasuk, Richard W. Hughes, Brendan M. Laurs, Ren Lu, Flavie Isatelle, Kenneth Scarratt, Emily V. Dubinsky, Troy R. Douthit, and John L. Emmett|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||09 Sep 2011 22:37|
|Last Modified:||09 Sep 2011 22:37|
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