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GIA Detects Composite With CVD Layer Grown Over Natural Diamond

GIA / ROBISON MCMURTRY

A 0.64-carat fancy greyish-greenish-blue cushion modified brilliant-cut diamond was recently found by the Gemological Institute of America (GIA) to be a composite consisting of a natural yellowish colour diamond with a layer of chemical vapour deposition (CVD) synthetic diamond that had blue and grey colour components, grown on top of it.

GIA research associate Troy Ardon and analytics technician Garrett McElhenny who reported the finding in Spring 2019 edition of the GIA’s Gems & Gemology journal, calculated that the CVD layer was 200 microns thick and accounted for 0.1 carat of the stone’s total weight.

Ardon and McElhenny concluded in their article, “With the second of these composites seen at GIA, this could be a new type of product entering the market. Earth-grown diamonds with synthetic diamond grown on the surface require extra scrutiny due to the presence of natural-looking features, both spectroscopic and gemological. Careful inspection still reveals the presence of synthetic indicators, which expose the true nature of the diamond.”

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