Mumbai: The Gemological Institute of America (GIA) recently uncovered an unusually large number of undisclosed synthetic diamonds mixed in with natural melee diamonds, the lab confirmed with Rapaport News on Monday.

A parcel of 323 melee diamonds with an average size of 0.014 to 0.015 carats was found to contain 101 chemical vapor deposition (CVD) synthetic stones at the GIA’s Mumbai lab, reported Wuyi Wang, the institute’s director of research and development. The goods had been submitted to the GIA’s Melee Analysis Service, which made the discovery.

The GIA launched the service in December of last year and has regularly identified small quantities of undisclosed synthetic melee diamonds in some parcels submitted for analysis, Wang said.

However, he explained, “this is the first time we have seen such a significant percentage of CVD melee mixed with natural melee.”

Fewer cases of undisclosed mixing have been reported recently as more testing facilities and detection machines have come to market, Praveenshankar Pandya, chairman of India’s Gem & Jewellery Export Promotion Council (GJEPC), said at the World Federation of Diamond Bourses’ Presidents’ meeting last month.

The first major discovery of undisclosed synthetics was in May 2012, when several hundred CVD diamonds were sent to the International Gemological Institute ‎‎(IGI) in Antwerp and Mumbai to be certified as natural diamonds.‎

Still, concerns of such fraudulent activity are on the rise as synthetic diamond production increases, the GIA and De Beers International Institute of Diamond Grading & Research (IIDGR) said in separate presentations at last week’s Hong Kong Diamond, Gem & Pearl show.