Feature Gems & Gemology, Summer 2012, Vol. 48, No. 2

CVD Synthetic Diamonds from Gemesis Corp.

Gemological and spectroscopic properties of CVD synthetic diamonds from Gemesis Corp. were examined. Their color (colorless, near-colorless, and faint, ranging from F to L) and clarity (typically VVS) grades were comparable to those of top natural diamonds, and their average weight was nearly 0.5 ct. Absorption spectra in the mid- and near-infrared regions were free from defect-related features, except for very weak absorption attributed to isolated nitrogen, but all samples were classified as type IIa. Varying intensities of [Si-V]- and isolated nitrogen were detected with UV-Vis-NIR absorption spectroscopy. Electron paramagnetic resonance was used to quantify the neutral single substitutional nitrogen content. Photoluminescence spectra were dominated by N-V centers, [Si-V]-, H3, and many unassigned weak emissions. The combination of optical centers strongly suggests that post-growth treatments were applied to improve color and transparency. PL spectroscopy at low temperature and UV fluorescence imaging are critical in separating these synthetic products from their natural counterparts.