In the last few years, available colorless and near-colorless gem-quality synthetic diamonds have improved dramatically with advances in growth technologies and a heightened understanding of the underlying processes. Key features that reveal the samples’ HPHT synthetic origin are described. Their fluorescence and phosphorescence behavior was investigated using ultraviolet excitation from a long-wave/short-wave UV lamp, a DiamondView instrument, and a phosphorescence spectrometer. Infrared absorption analysis showed that all were either type IIa or weak type IIb, and photoluminescence spectroscopy revealed that they contained Ni-, Si-, or N-related defects. Importantly, 89% were classified as colorless (D–F), demonstrating that HPHT growth methods can be used to routinely achieve these color grades. These samples, with weights ranging from 0.20 to 5.11 ct, had color grades from D to K and clarity grades from IF to I 2. Forty-four faceted samples synthesized using modified cubic presses were analyzed using a combination of spectroscopic and gemological techniques to characterize the quality of the material and determine the means of distinguishing them from natural, treated, and alternative laboratory-grown diamonds. The Russian company New Diamond Technology is producing colorless and near-colorless HPHT-grown synthetic diamonds for the gem trade. Photo courtesy of New Diamond Technology.

The visual characteristics of these samples are summarized in table 1. B: Sample NDT-A, a 5.11 ct specimen with K color, is the largest faintly colored synthetic diamond studied by GIA to date. From left to right, samples NDT04, NDT02, and NDT01 weigh 2.02, 2.20, and 2.30 ct, respectively. A: These three colorless HPHT-grown synthetic diamonds demonstrate some of the sizes achieved by New Diamond Technology. Manage Your GIA Alumni Association™ Membershipįigure 1. Comprehensive CAD/CAM For Jewelry Certificate

Diamond dimensions 260