Thai Gem Treaters Dispute Labs

The Chanthaburi (Thailand) Gem and Jewelry Association (CGJA) met with local gem heaters on June 8 to develop a response after two major gem labs—the American Gem Trade Association’s Gem Testing Center (AGTA GTC) and the Gemological Institute of America’s Gem Trade Laboratory (GIA GTL)—decided to add the term “bulk diffusion” to descriptions of the new heat-treated yellow and padparadscha-like sapphires coming out of Thailand.

Following the daylong meeting, CGJA announced that it disputed the findings of the four international labs at the forefront of the controversy—AGTA GTC, GIA GTL, Gübelin Gem Lab, and SSEF. Although Gübelin and SSEF call the new enhanced gems simply “treated sapphire,” CGJA accused all four labs of describing the new heat-treated material with “unjust criticism and hasty conclusions.”

CGJA says the four labs are “unqualified” to make these identifications and accuses them of having “effectively stymied the legitimate business that developed involving these materials.” It notes that “some 90% of the corundum traded during the past 20 years has involved heated material. Heating processes have resulted in the improvement in the value of many gemstones, through the permanent enhancement of their color and clarity.”

The organization says the labs “are ignorant as to the importance of the new heating techniques” and calls their opinions “somewhat theoretical.”

The theory they refer to is that the orange-pink sapphires are the result of heating pink Madagascar sapphires in the presence of chrysoberyl (BeAlO4). It’s believed that beryllium and other elements from the chrysoberyl enter the sapphire and react with the elements already inside, which causes the color enhancement.

According to CGJA and the Chanthaburi heat-treaters, chrysoberyl alone cannot change the color of the sapphire: “Heating pink sapphires in the presence of oxygen and chrysoberyl, both of which are colorless, only results in color change in some instances, and the results are extremely varied. All present agreed that this color change must be a result of chemical reactions involving elements already contained within the gems.”

Thus, CGJA believes that labeling the gems “bulk diffused” or “treated sapphires” is erroneous because it implies “the addition of an external agent.” But what GIA and AGTA said is that it is because of the chrysoberyl elements diffused into the sapphire that the gem changes color—the chrysoberyl does not itself impart the color, but it does provide the means to color enhancement. In either case, the term “bulk diffusion” still applies.

The Thais maintain that the labs’ “shortsighted discrediting of new heating techniques will only affect the long-term viability of the international gem industry.” But some U.S. gem industry leaders believe that nondisclosure of the new heat treatment has the potential to undermine the entire corundum market worldwide.

“This diffusion episode is only the latest in a series of credibility crunches that began in Thailand in the 1960s,” writes Cap Beesley of the American Gemological Laboratories in New York. “Heat-treated blue and yellow sapphires, fracture filling of rubies, and the Mong Hsu masquerade have never been accompanied by meaningful disclosure.” Beesley continued, “Historically, we have always found a reputable contingent from the Thai community that were sensitive to the long-term impact of inadequate disclosure policy. This respectable segment of Thai stone dealers and treaters should challenge their counterparts to be more open and responsive.”