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Tairus, in Novosibirsk, has produced yet another new type ofRussian hydrothermal synthetic emerald, now being marketed in Bangkok. Examination of eight fac eted samples revealed that, with the exception of certain characteristic inclusions, the basic gemological properties shown by this new synthetic are essentially the same as those enco untered in other hydrothermally grown synthetic emeralds and some natural emeralds. If the characteristic inclusions are not present, distinctive spectral characteristics in both the mid-and near-infrared regions ofthe spectrum will serve to separate these synthetic emeralds from their natural counterparts. The first commercially successful hydrothermal synthesis of beryl is generally attributed to Johann Lechleitner wh o, in 1960, produced hydroth erm al ABOUT THE AUTHORS Mr. Koivula is chief research gemologist, the late Mr.

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Blue diffusion-treated sapphires are becoming more prevalent than ever before. The diffusion technique, which involves the addition of color-causing chemicnls during heat trentment, results in a thin layer of color at the surface of colorless or light-colored sapphire. The color was found to be stable to routine cleaning procedures; however, it may be partially or completely-removed if the stone is repolished pf, recut. Recently, significant quantities o f so-called "deep" diffusiontreated sapphires have entered the market. This article documents the properties of these and other blue diffusion-treated sapphires, and presents means o f identifying this method using simple gemological tests.

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