Near-Colorless HPHT Synthetic Diamonds from AOTC Group

The gemological and spectroscopic properties of 52 colorless to fancy light-colored HPHT synthetic diamonds (40 of them colorless or near-colorless) produced by AOTC using either toroid-or BARS-press technologies were characterized.In addition to achieving excellent color grades, these commercially available faceted synthetics had a weight range of 0.05 to 0.80 ct, and possessed IF to I 2 clarity.Their synthetic origin may be difficult to determine with standard gemological techniques alone, but they were conclusively identified using advanced testing methods, including photoluminescence, FTIR spectroscopy, and fluorescence imaging.Inclusions in two samples, grown by different press types, were studied using LA-ICP-MS.The trace-elemental analysis results indicated that the inclusions formed by the trapping of the solvent/catalyst melt during synthesis.Analysis of the combined multi-technique data provided insight into the identities of the solvents, catalysts, and nitrogen getters possibly used to grow high-quality HPHT synthetic diamonds.the gem trade, natural diamonds with D to Z I n color are significantly more abundant than their fancy-color counterparts.The opposite is true for gem-quality synthetic diamonds, where near-colorless specimens are more challenging to produce.Most synthetic diamonds used for jewelry are produced by either high-pressure, high-temperature (HPHT) or chemical vapor deposition (CVD) techniques.Advances in CVD technologies, as well as an improved understanding of the growth processes, led to the introduction of near-colorless CVD synthetic diamonds around the middle of the last decade (Wang et al., 2007) by companies such as Apollo Diamond Inc. (sold in 2011 to Scio Diamond Technology).More recently, the near-colorless CVD synthetic diamond market has expanded with the large-scale production from Gemesis Corporation, which reportedly applies color-enhancing post-growth treatments to its as-grown material (Wang et al., 2012a).CVD synthetics have garnered significant publicity based on instances where samples have been submit-See end of article for About the Authors and Acknowledgments.