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 Be diffusion 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.
DATA DEPOSITORY
Table 1: Samples Used for Gemological Characterization
Table 2: Trace-Element Compositions of Be-Diffused and Natural-Color Corundum Determined Using SIMS (ppma)
Submitted by Wuyi Wang
Prepared by Gems & Gemology staff
July 30, 2003
Table 3: Durability and Stability of the Treatment in Be Lattice Diffusion–Treated Orange to Pinkish Orange Sapphires
Submitted by Robert E. Kane
Prepared by Gems & Gemology staff
July 30, 2003
Supplementary Bibliography on Corundum Diffusion
Prepared by Gems & Gemology staff
July 30, 2003
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 Be diffusion 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.
DATA DEPOSITORY
Table 1: Samples Used for Gemological Characterization
Table 2: Trace-Element Compositions of Be-Diffused and Natural-Color Corundum Determined Using SIMS (ppma)
Submitted by Wuyi Wang
Prepared by Gems & Gemology staff
July 30, 2003
Table 3: Durability and Stability of the Treatment in Be Lattice Diffusion–Treated Orange to Pinkish Orange Sapphires
Submitted by Robert E. Kane
Prepared by Gems & Gemology staff
July 30, 2003
Supplementary Bibliography on Corundum Diffusion
Prepared by Gems & Gemology staff
July 30, 2003
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