GIA can detect troublesome stones, McClure says

GIA has made “considerable progress” in detecting diamond treatments and synthetics, Gemological Institute of America director of West Coast identification services Shane McClure said in a seminar Thursday.

“Figuring some of these things out is still a challenge, though we’ve made progress,” McClure said. “We have a lot of work to do.”

Jewelers should look out for:

• HPHT-treated diamonds typically have both high color and clarity. That’s because the treating conditions are so extreme, some included stones don’t survive the treatment.

• Most treated diamonds are inscribed, but, McClure said, “The inscriptions can be removed, and they are occasionally.”

• Other indicators of HPHT treatment include frosted feathers, a heat-damaged surface, tension fractures and graphitization of inclusions.

• GIA has a database of 10,000 HPHT-treated stones, though some stones can still be a problem for gemologists. “If you have a flawless diamond that’s Type IIa, you have to send it to a laboratory,” McClure said.

• Internal laser drilling is a new kind of laser drilling that’s harder to see, since it leaves no surface-reaching hole. Sometimes it also produces feathers, McClure said, which makes its usefulness questionable.

• The quality of synthetics is improving. Among the characteristics of synthetics are internal color-zoning patterns, distinctive clouds of pinpoints, distinctive fluorescence patterns, and metallic inclusions, which can make them magnetic. “With careful examination, most stones can be identified by gemological means,” he said.

• There are not many synthetics on the market. “The material is still in its experimental stage, not on the market at this time, so there is no need to panic, not that there is a reason to panic in any case.” He said many of the stones labeled as synthetic diamonds on the Internet are really imitations.