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Melee Parcel Contains Just One Natural Stone
Aug 16, 2018 10:24 AM
By Rapaport News
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RAPAPORT...
The Gemological Institute of America (GIA) found just one
natural diamond in a melee parcel containing more than 1,000 undisclosed
synthetic stones, according to a recent lab note.
The organization’s New York center received 1,102 small
diamonds weighing a combined 9.67 carats for its melee-analysis service.
Initial screening referred 1,093 of them for further testing, while the GIA
could not assess the other nine because they did not meet the service’s
criteria for examining stones.
Spectroscopic tests confirmed 1,092 of the 1,093 diamonds
to be synthetics created using the High Pressure-High Temperature (HPHT)
technique. This case represents the largest percentage of undisclosed synthetic
melee the GIA has seen in a parcel, researchers Stephanie Persaud, Wuyi Wang,
Paul Johnson and Ivana Petriska Balov wrote in the summer 2018 issue of Gems
& Gemology, the institute’s journal.
“The increase in the amount of synthetic melee submitted
— both disclosed and undisclosed — to GIA’s laboratories for identification has
exponentially increased since GIA began offering its melee-analysis service in
2016,” the team wrote.
More commonly, the GIA receives bags of melee containing
a mixture of natural and lab-grown diamonds, or with just a few synthetics — a practice
known in the trade as “salting,” the researchers said.
One notable characteristic of the latest melee batch was
the absence of nickel, a catalyst that manufacturers often use in the HPHT process,
the team wrote. Gemologists did not detect the element when they put the
material through the spectroscopic examination.
“The majority of the HPHT synthetic melee had no
detectable traces of [nickel], demonstrating the importance of advanced testing
to identify these melees,” the authors added.
Image: Sood Oil (Judy) Chia and Towfiq Ahmed/GIA
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Tags:
Gemological Institute of America, GIA, grading, lab-grown diamonds, melee, Rapaport News, Small diamonds, Synthetic diamonds, Synthetics, undisclosed synthetics
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