GIA Spots Moissanite Mimicking Diamond – Twice

Two pieces of synthetic moissanite imitating diamonds have turned up at the Gemological Institute of America (GIA), underlining the risk of confusion between the two materials.

In the first case, someone submitted a 7.42-carat, light-bluish-green rough stone to the GIA New York laboratory for a colored-diamond identification and origin report. Staff members identified it as a synthetic moissanite crystal that had been carved to resemble a natural rough diamond, GIA analytics technicians Courtney Robb and Sarah Arden wrote in the fall 2022 issue of Gems & Gemology, the institute’s scientific journal.

Whoever carved the moissanite chose specifically to fashion an octahedron shape to mimic a natural rough diamond. They even gave it stepped edges and coarse textures to resemble a diamond that had been partially resorbed by kimberlitic magma. “Sharp and well-formed” diamond octahedra are rare because they are usually exposed to corrosive kimberlitic fluids in the earth’s mantle, the researchers explained.

“This investigation is a reminder to take caution when identifying gemstones, as intentional material processing steps such as these may be used to deceive consumers and could damage the integrity of the gem trade,” they noted.

In the second case, GIA Mumbai received a square modified brilliant, 1.71-carat stone for a report update service, only to find that the girdle inscription was fake. The etched code — which featured the letters “GIA” — matched a real GIA report for a square modified brilliant, 1.71-carat natural diamond. However, the font was not the same as for a genuine GIA inscription, and further gemological examinations confirmed that the polished stone was synthetic moissanite, wrote Shoko Odake, senior manager of identification at GIA in Tokyo, in the same journal edition.

Synthetic moissanite — the only type of gem-quality moissanite readily available — is a likely option for fraudsters. It resembles diamond “at a glance” and has a similar specific gravity and “heft,” Robb and Arden added. This means two pieces of the respective materials with the same volume will have weights quite close to each other.

Main image: Graders at the GIA. (GIA)