THE CHINESE RED FELDSPAR CONTROVERSY:
CHRONOLOGY OF RESEARCH THROUGH JULY 2009
-George R. Rossman
This article is included in the Spring G&G 2011 available as an online or print subscription from GIA. I have just finished reading the 15 page pdf. This is copyrighted material available by subscription only, so I am unable to reprint or post a link.
The article is what the title states; the details of the results and testing performed by Dr. Rossman, with reference to a few others, up to 2009. He includes many images and charts outlining his observations and test results.
Rossman states the following in a box titled, "Need To Know":
• Studies from 2002 to mid-2009 show that red (and green) Cu-bearing andesine-labradorite reportedly from Tibet, “China,” and the Democratic Republic of the Congo have overlapping chemical and physical properties.
• Traces of copper-containing fluxes on the surface of rough stones and argon isotopic measurements indicate these feldspars have been heated to high temperatures in the presence of Cu.
• Evidence up to mid-2009 suggests that laboratory diffusion of Cu into pale yellow feldspar from Inner Mongolia (but not Mexico) could account for some or all of the “Asian/Congolese” feldspar in the market.
• This does not eliminate the possibility that andesine deposits in Tibet that were documented in 2010 are genuine.
A bar graph included in the article measuring the weight percentage of K2O (Potassium oxide) shows Tibet, Congo and China having uniformly high levels(almost identical), Mexico in the mid range and Oregon being lowest.
In an SEM graph with a high magnification image of the surface of one of the treated stones tested, Rossman shows the highly elevated levels of Copper and Potassium contained the the glassy flux residue on the stone and compares those levels to the much lower levels of both in the stone.
In closing his report, Rossman makes the following statements and observations:Regarding Congo
It was subjected to argon-isotopic studies in July 2009, and fell within the same range as samples stated to be from Tibet and China (table 2). Furthermore, its chemical composition matched the treated Tibetan/“Chinese” feldspar (see G&G Data Depository). These results clearly raise doubts that there is a Congolese source of natural red andesine.Summary through mid-2009
The argon-isotope results offer the most compelling evidence of widespread high-temperature treatment of Tibetan/“Chinese” andesine. Coupled with the observation of what appear to be copper containing fluxes on the surface, and the occasional microscopic bits of copper compounds attached to the stones, the case for copper- diffused andesine from Inner Mongolia is strong. In fact, according to Christina Iu (pers. comm., 2011), it is now freely admitted by some Asian dealers. Nevertheless, this does not eliminate the possibility that there is also a source of natural-color andesine in Tibet, and samples obtained from a subsequent expedition in September 2010 (e.g., Abduriyim and Laurs, 2010) have been the focus of further research that will be reported in a future article.
Although the 2010 samples and testing were discussed during the GILC conference, I am unable to publish that information without breaking the confidentiality agreement I signed. As Rossman has stated in his article, further research was being conducted on these samples by a group of scientists present during the conference and their report should be forthcoming.