Over the past two years, the heat treatment of corundum involving lattice diffusion of beryllium (Be) at temperatures over 1800°C has become a major issue in the gem trade. Although initially only orange to orangy pink ("padparadscha"-like) sapphires were seen, it is now known that a full range of corundum colors, including yellow and blue as well as ruby, have been produced or altered by this treatment. An extension of the current understanding of the causes of color in corundum is presented to help explain the color modifications induced by Be diffusion. Empirical support is provided by Bediffusion experiments conducted on corundum from various geographic sources. Examination of hundreds of rough and faceted Be-diffused sapphires revealed that standard gemological testing will identify many of these treated corundums, although in some instances costly chemical analysis by mass spectrometry is required. Potential new methods are being investigated to provide additional identification aids, as major laboratories develop special nomenclature for describing this treatment.

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demonstrated its ability to grow single-crystal CVD synthetic diamonds of moderate gem quality several years ago (Wang et al., 2003). For the most part, the samples examined in 2003 were relatively small and of limited thickness for faceting purposes. Nearly all of these early crystals were predominantly brown with varying degrees of saturation. Colorless CVD-grown diamonds, both nitrogen doped and high purity, were also synthesized by LIMHP-CNRS in France (Achard et al., 2005;Wang et al., 2005), but the reported crystals were usually

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