Mumbai--The Gemological Institute of America recently screened a parcel of diamond melee and found that nearly a third of the stones were undisclosed synthetics.

The GIA confirmed to National Jeweler that of a parcel containing 323 diamonds, 101 were lab-grown stones. The parcel had been submitted for screening to the GIA’s Mumbai lab and the diamonds were detected using the GIA’s new melee diamond analysis service.

The GIA launched its melee diamond analysis service in December last year. The fully automated system screens between 1,800 and 2,000 stones an hour, separating natural, untreated stones from treated and lab-grown ones, both HPHT (high-pressure, high-temperature treatment) and CVD (chemical vapor disposition).

The service also separates diamonds by color range.

The 101 synthetic diamonds caught in Mumbai were grown using the CVD process, the GIA said.

For its melee analysis service, the GIA accepts round D to Z diamonds from 0.90 to 4.00 mm in size, or roughly 0.005 to 0.25 carats.

Since introducing the melee screening service in most of its labs worldwide, this is the first time the GIA “has seen such a significant percentage of CVD melee mixed with natural melee,” a spokesperson told National Jeweler.

The GIA declined to comment when asked if they believed the inclusion of the undisclosed lab-grown stones was intentional or if they would pursue any type of action against the submitter.

The detection of lab-grown melee is one of the biggest challenges facing diamond grading labs today, as they work to develop machines that can quickly and cost effectively screen small stones.

In addition to the GIA’s recently launched melee screening service, De Beers just introduced the second, substantially cheaper version of its Automated Melee Screener.

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