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GIA Spots Natural Diamond with CVD Blue Layer
May 4, 2017 4:14 AM
By Rapaport News
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RAPAPORT... The Gemological Institute of America (GIA) has found a
natural diamond with a synthetic coating that tints it blue – and has warned that
more such hybrids might be on the market.
The 0.33-carat stone, which had been graded fancy blue, had
a thin layer of lab-grown diamond on it, created using chemical vapor
deposition (CVD), the GIA explained in a lab note this week. It was the GIA’s
first such discovery.
Gemologists at the GIA’s New York lab noticed a number of
unusual characteristics that gave away the diamond’s synthetic coloring. The
stone contained both nitrogen and boron defects — a rare combination. They also
found it was a mixed type Ia and IIb diamond, another highly uncommon scenario.
Analysis using the DiamondView imaging machine showed the diamond itself had
characteristics of a natural stone, but the top layer bore signs of being
manmade.
While the GIA had never before found a synthetic overgrowth
on a natural diamond with a fancy-color grade, the lab warned that there were
probably more cases out there undiscovered.
“Identification of colored diamonds should be performed very
carefully by looking for unusual characteristics, such as a straight boundary
line associated with an interface plane, and fluorescence zones with sharp
edges in DiamondView images,” the GIA said in the note. “Examination of this
fancy-colored composite diamond indicated that similar challenges could exist
for colorless and near-colorless diamonds.”
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Tags:
chemical vapor deposition, cvd, fancy-color diamonds, GIA, Natural Diamond, Rapaport News, synthetic coating, Synthetic diamonds, Synthetics
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