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The Chinese Red Feldspar Controversy: Chronology of Research Through July 2009

Rossman, George R. (2011) The Chinese Red Feldspar Controversy: Chronology of Research Through July 2009. Gems and Gemology, 47 (1). pp. 16-30. ISSN 0016-626X. http://resolver.caltech.edu/CaltechAUTHORS:20110603-091944283

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Abstract

Red copper-containing plagioclase feldspar from Oregon has been available for over a century. In the early 2000s, new localities for copper-bearing feldspar were reported from the Democratic Republic of the Congo and from Tibet or an unspecified locality in China. The new material has been the subject of widespread concerns about its geographic origin and natural color. In fact, extensive studies of its composition, spectroscopy, physical appearance, and isotopic properties suggest that much of the red andesine on the market is the product of laboratory diffusion of copper into pale yellow andesine from Inner Mongolia. All samples initially subjected to testing as part of this study gave strong evidence or suggestions of treatment. Traces of copper-containing fluxes found on rough stones, and measurements of argon isotopic composition in particular, demonstrate that the tested material was recently heated to high temperatures under conditions where copper diffusion could occur. These results apply to samples that were obtained through July 2009, but do not include samples from expeditions to Tibet in 2010.


Item Type:Article
Related URLs:
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http://www.gia.edu/research-resources/gems-gemology/issues/spring2011-contents/spring-2011-rossman.htmlPublisherUNSPECIFIED
ORCID:
AuthorORCID
Rossman, George R. 0000-0002-4571-6884
Additional Information:© 2011 Gemological Institute of America. Assistance with the electron microscopy was provided by Dr. Chi Ma of the California Institute of Technology (Caltech). Critical to the argon studies was the support of Dr. Ken Farley and his technical staff at Caltech. Dr. John Beckett at Caltech assisted with the diffusion experiments. The generosity of the numerous donors who collectively provided many thousands of samples is highly appreciated. Significant donations were provided by a Bangkok dealer who wishes to remain anonymous, Art and Marc Garabedian (Direct Shopping Network, Glendale, California), Shawn Sullivan and Jerry Sisk (Jewelry Television, Knoxville, Tennessee), William Larson (Palagems.com, Fallbrook, California), Jacqueline Li (Do Win Development Co. Ltd., Tianjin, China), Dr. Laurent Sikirdji (GemFrance, Saint Ismier, France), Gwen Sadler (Ion International Inc., Calabasas, California), Mark Kaufman (Kaufman Enterprises, San Diego, California), Dr. Ahmadjan Abduriyim (formerly with the Gemmological Association of All Japan–Zenhokyo, Tokyo, Japan), Dr. John Emmett (Crystal Chemistry, Brush Prairie, Washington), Dr. Emmanuel Fritsch (University of Nantes, France), Shane McClure (GIA Laboratory, Carlsbad), Julie Chen (Andegem, Los Angeles), Chris Rose (High Desert Gems & Minerals, Reno, Nevada), Mariana Photiou (San Francisco), Chris Johnston (Johnston- Namibia C.C., Omaruru, Namibia), Robert Rogers (Rogers mine, Lake County, Oregon), Bill Barker (Barker and Co., Scottsdale, Arizona), Doug Wallace (Mineral Search Inc., Dallas), Karla Proud (Exotic Gemstones, Bend, Oregon), Smithsonian National Museum of Natural History (Washington, DC), Dr. Barkley Kamb (Caltech), and Dr. Jim Gutmann (Wesleyan University, Connecticut). Christina Iu (M.P. Gem Corp., Yamanashi, Japan) is thanked for providing helpful information. Partial funding for this project was provided by Andegem and the White Rose Foundation (Sunnyvale, California).
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Andegem UNSPECIFIED
White Rose Foundation, Sunnyvale, CaliforniaUNSPECIFIED
Record Number:CaltechAUTHORS:20110603-091944283
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20110603-091944283
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23892
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Jun 2011 17:23
Last Modified:06 Feb 2017 21:07

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