New York Lab Issues Warning About CVD Diamonds

The CVD stones were also made using different parameters and reactors providing evidence they came from different facilities.

The New York gem lab Analytical Gemology & Jewelry (AG&J) has issued an alert about CVD diamonds being sold as natural, type IIa brown stones.

A parcel of such stones was recently submitted by a customer as natural HPHT-treated diamonds. However, they contained 75 percent CVD-grown HPHT-treated diamonds. The diamonds were bought from someone in the diamond trade with whom the AG&J client had a long-standing business relationship.

AG&J said a parcel of 18 diamonds, with 17 being round and one being a marquise-cut, weighing a total of six carats, ranging in size from 0.14-carat to 0.635mm, color ranging from F to gray and a clarity range from VVS to SI, was submitted to the lab at the end of July.

AG&J identified 13 CVD-grown HPHT-treated synthetic diamonds.

The stones were purchased in Mumbai as type IIa brown diamonds. The buyer used a portable FTIR instrument to test the stones during the purchase and to make sure the diamonds were type IIa or very low nitrogen type Ia stones intended for HPHT treatment.

The client became suspicious after the HPHT treatment did not provide the required results. Several stones turned gray, while the highest color was only I.

The CVD stones were also made using different parameters and reactors providing evidence they came from different facilities.

“It was not surprising that the client could not detect the CVD diamonds using FTIR spectroscopy,” said AG&J's CEO, Dusan Simic, “as this requires more sophisticated methods that also have to keep up with changes in the production of CVD and HPHT-grown stones as well as all treatments.”