What makes a good synthetics detector?

Joshua Freedman

The massive project by the Diamond Producers Association (DPA) to test 18 lab-grown detectors has raised an important question: What should you look for in such a machine?

Accuracy is, of course, a major part of the equation (alongside speed, price and usability), but it isn’t a clear-cut issue. The first set of results from the DPA and Signet Jewelers’ Assure Program, which came out last week, gave up to nine different performance scores for each scanner, reflecting their varied abilities.

The criteria don’t all apply to every machine, as only five of them can conclusively detect lab-grown diamonds, while six merely claim to refer questionable stones for further checks. The other seven are still undergoing testing.

Definitely natural

The DPA believes the most important factor is the ability to verify that a diamond is natural, rather than being able to say that a stone is definitely synthetic or definitely a simulant. It calls this key metric the “diamond false-positive rate.” The good news is that all but two devices scored 0%, indicating they didn’t mistakenly label any man-made stones as natural. (See the list at the end of this article.)

“It’s a reflection of the instrument’s ability to ensure that only natural diamonds are verified as natural diamonds,” said Jean-Marc Lieberherr, CEO of the DPA. “From a consumer perspective, this is the primary function of a diamond-verification instrument.”

Consumers expect retailers to give formal reassurances that their products are what they say they are, and those are only as reliable as the detection machines the retailer or supplier used, Lieberherr explained. Out of all the associated risks, the main one is that a synthetic diamond should mistakenly be sold as natural, he added.

Refer: a friend? 

That measure is far from the only important one. A machine that’s overly strict, wrongly referring some natural diamonds for further testing, might be good if you want to be sure you’re left with only natural stones. But those additional tests may be expensive. You might need to buy more than one machine. Plus, a buyer who receives a batch of natural diamonds and finds that some of them can’t be verified may grow unnecessarily suspicious of his or her supplier.

That’s why some traders may also look at the “diamond referral rate,” which is the percentage of natural stones that a machine categorizes as undetermined (“refer”). Again, 0% is the best, with only one instrument — De Beers’ DiamondView — achieving that. Some machines didn’t get a score, as they don’t classify stones as “refer.”

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Source Rubel & Ménasché