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Stargems brings the DaVinci system to Botswana

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GSI discovers inconsistent lattice defects in CVD growth process

29 september 2022
Recently a CVD lab-grown diamond weighing 1.547ct., emerald cut, VS1 clarity and H colour was submitted to the Gemological Science International (GSI) Mumbai Lab for Post Growth Treatment Identification, which revealed interesting results says GSI.
The absorption spectra in the mid-infrared region showed typical absorption features of type IIa, as seen in CVD lab-grown diamonds. No additional absorption features were observed. Photoluminescence spectroscopy with 532 nm excitation showed peaks at 737, 637 and 575 nm. The 737 nm and766 nm emission systems are associated with silicon-vacancy centres, including moderately strong NV emission lines at 575 and 637 nm.
Raman microscope with 532 nm spectrometers showed extremely strong NV emission lines at 575 and 637 nm, the absence of 596/597 nm doublet indicates post-growth treatment.
DiamondView revealed a strong greenish-yellow fluorescence when observed length-wise, and interestingly, on a rotation of 180 degrees, strong orange fluorescence was observed. 
Due to prolonged observation in DiamondView, when the DiamondView was turned off, an intense red phosphorescence for a few milliseconds (10-15 milliseconds) was observed which quickly changed to yellow. 

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Image credit: GSI

Such observations have not been reported earlier in CVD diamonds. This intense red phosphorescence was observed only after prolonged exposure to DiamondView.
The possible reason for different fluorescence colours, in different directions and phosphorescence, is assumed could be due to inconsistent lattice defects during the CVD growth process.

Aruna Gaitonde, Editor in Chief of the Asian Bureau, Rough&Polished