Bulk Diffusion Is Identifiable

The Gemological Institute of America's Gem Trade Lab (GTL) and the American Gem Trade Association's Gem Testing Center (GTC) have announced progress in identifying bulk-diffusion-treated sapphires coming from Chanthaburi, Thailand. It now appears that much of this new material can be identified with standard gemological tests. Gemologists will have to use magnification, immersion, and possibly visible spectrum. "We're looking for color distribution, primarily," says Ken Scarratt, GTC's director in New York. "Surface conformal zoning. We do see this in a lot of these stones." The layer is difficult to find in the new stones, even under immersion. "In some cases, the color zoning is really quite deep, but it is still there," says Scarratt. In addition, heated inclusions may be indicators, and the visible spectrum also might offer clues. Meanwhile, other gemological tests are being inve

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