The Rough Impostor

We've all read about lab grown diamonds being passed off as natural stones, being cut as an exact match, with the same inclusions and even bearing what appears to be a genuine inscription.

So much for polished stones. Now it seems bad actors are trying it with rough.

It's far harder to do. To fool a lab they'd have to simulate not just the material but the stone's entire geological history. The rewards could be significant.

GIA was recently asked to identify a 6.87-carat, near-colorless crystal that turned out to be a CVD lab grown.

It would have been worth perhaps $20,000 to $40,000, depending on clarity and market conditions, if genuine.

GIA noted that producing such a stone from a CVD block would have required careful processing and would have yielded a significantly smaller polished diamond than cutting directly from the as-grown block.

"The only motivation for such an action appears to be a deliberate attempt at deceit," said the authors of a report on the CVD rough, which appeared in GIA's Gems & Gemology.

The fraud almost certainly depended on the stone never reaching a laboratory, because that is where the deception would inevitably collapse, as it did in this case.

X-ray diffraction exposes the wrong crystallographic orientation, microscopy reveals polishing lines instead of natural growth features, infrared spectroscopy flags the Type IIa spectrum (well-formed natural octahedrons are almost always type Ia), and DiamondView imaging, which uses deep ultraviolet light, displays the unmistakable luminescence patterns of CVD growth: orange stratified bands and blue dislocation plumes.

A natural rough diamond is a geological artifact, shaped over millions of years under extreme pressure and temperature. Every aspect of its appearance, its shape, its surface texture, its internal features, records that history.

A lab grown is produced in a matter of weeks inside a machine, and the resulting crystal has a different internal structure, different growth patterns and different surface features.

To pass a lab grown stone off as natural rough, a fraudster must ensure the shape matches nature, the surface looks natural, the chemistry fits, and the growth history is visible under UV.

Is it worth not only the effort, but also the wasted carats? Perhaps the most powerful economic deterrent is the yield penalty. CVD diamonds are grown as blocks or plates optimized for cutting into polished gems.

To make one look like rough, they must cut away material to impose a crystal shape, then cut it again to recover a polished stone.

GIA's authors noted that this would be difficult and wasteful, producing a significantly smaller polished diamond than cutting directly from the as-grown block.

Despite these hurdles, the incentive remains. The price gap between natural and lab grown is widening.

The reward is greatest where the stone appears to offer an attractive cutting proposition: a clean, near-colorless crystal with a credible octahedral outline and a size large enough to attract attention.

GIA's authors say there is "currently no evidence of any widespread switching of synthetic for natural diamonds in the rough diamond pipeline".

This case has attracted attention exactly because it's a rarity. And because the perpetrators were caught out. The entire logic of such a fraud rests on the stone never being tested.

Can we expect a flood of similar cases? Probably not. Has there already been a flood of similar cases? It's entirely possible that some have slipped through, if the buyer hasn't had the stone checked, but again, probably not.

Have a fabulous weekend.