In mid-1988, I again began to see surface-diffusion treated corundums, or SDTCs, in Bangkok, but this time with a more sinister glint. It had always been in the back of my mind that, rather than taking near-colorless sapphires and treating them to a deep blue, some day treaters were going to take a stone which already had a lot of color of its own and just give it, via surface diffusion, a bit more. This is what happened in mid-1988 – to such an extent that I reported the matter to the International Colored Stone Association.
Treaters were taking medium-quality Kanchanaburi sapphires that had a lot of color of their own, but were heavily zoned, and diffusing their problems away.
Because certain burners were disappointed that their best efforts could still be identified, they embarked upon a campaign of threat and innuendo against Bangkok gemologists. But this had little effect, eventually giving way to…
Treaters were taking medium-quality Kanchanaburi sapphires that had a lot of color of their own, but were heavily zoned, and diffusing their problems away.
Because certain burners were disappointed that their best efforts could still be identified, they embarked upon a campaign of threat and innuendo against Bangkok gemologists. But this had little effect, eventually giving way to…
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