New York City-based Analytical Gemology & Jewelry recently received a parcel containing more than 200 undisclosed synthetic yellow melee diamonds.

Using its proprietary melee screening process, AG&J was able to determine that a 4,556-stone, 56 ct. parcel, sent to the lab in December, contained 243 synthetic yellows. The remainder of the batch was natural and untreated.

The stones ranged in size from 0.7 mm to 2.5 mm, with colors ranging from fancy intense yellow to vivid yellow with a brownish modifier. Clarity grades landed in the VS to SI range.

Photo courtesy of Analytical Gemology & Jewelry

“I was surprised to find so many,” says AG&J CEO Dusan Simic. “This was a very expensive lot, with a lot of nice colors. Someone deliberately mixed the right stones in, and it seems like they were trying to fool people.”

The stones also displayed low magnetism, another possible sign, Simic says, of deliberate misrepresentation, because magnetism is generally an easy indicator of synthetics.

The stones were all produced with the HPHT process, and Simic guesses they originated from China, where a lot of industrial diamond presses are based.

Simic’s lab has developed a mass screening process that can detect synthetics and treatments in melee. He is also working on a process that can spot synthetics in mounted melee.

De Beers also says it is working on a device that can spot treatments in smaller stones.

JCK