Diamantaires concerned as AMS mistakes natural diamonds for synthetic

Elena Levina

Six months have passed since De Beers unveiled a revolutionary device for detection of small synthetic diamonds – the Automated Melee Screening Device (AMS). However, initial results produced by the use of this device designed to protect the market from lab-made stones are not very reassuring. In the opinion of diamantaires using the device, they are now faced with the opposite problem: AMS identifies some part of natural diamonds as being synthetic.

Those who intend to buy an expensive stone can hardly incur the danger of purchasing a synthetic diamond instead. As a rule, diamonds over 0.5 carats in size have a certificate confirming their origin. The most vulnerable category among diamonds has long been melee or stones weighing from a few hundredths to 0.2 carats, which are widely used to manufacture mass-market jewelry. Their value is too small to check every stone in a parcel. As a rule, most diamantaires check only a few stones from a melee box, while some do not check at all. That is why it is rather easy to add synthetic diamonds to a parcel of melee: over the past two years, the most scandalous stories about “peppered” diamonds were mostly associated with small stones.

However, at that time the market simply had no device to perform rapid and inexpensive tests of small diamonds. This made some diamantaires just helplessly point to this hopeless situation, while others used it to freely sell synthetic diamonds under the guise of natural. The debut of AMS was greeted with a standing ovation from the market. AMS is not intended for sale, as other devices developed by De Beers – the company offers these devices to its sightholders to be used for a fee. The corporation has never disclosed the list of clients who received this device for further use. In the first few months, some of them proudly talked up about starting to operate AMS themselves, but by the end of the year the buzz around the device completely subsided, and the initial enthusiasm of its users apparently diminished.

The operating mode of AMS is based on spectroscopic examination – the device is used to assess the level of light absorption in different parts of the diamond. More than 95% of natural diamonds have inclusions of nitrogen (the so-called Type I diamonds), which gives a fingerprint spectroscopic picture pointing to their natural origin. At the same time, it is technologically extremely difficult to create a synthetic diamond containing the same kind of nitrogen inclusions.

The problem is in the remaining few percent. In nature, one may also come across natural diamonds devoid of nitrogen impurities, which are attributed to Type IIa. According to research data, diamonds belonging to Type IIa are found in almost all of the existing large diamond fields, regardless of their geographic location. Statistically, most often they are seen in the mines of Australia, Canada, Russia and in the south of Africa – that is, essentially, they can be purchased from any of the “big four” producers. “We used AMS to examine our stocks and were surprised to find a significant number of “synthetic” stones,” says one of the sightholders using AMS. “Our surprise was even greater when we checked our import certificates: most of these stones were purchased first hand from mining companies at their tenders.

Diamantaires, who buy small roughs, Type IIa from mining companies, are not at risk – being the first-hand buyers, they know the origin of their stones. However, there is a threat for all the other participants down the sales chain, who use this rough to manufacture polished diamonds and jewelry goods. Due to the absence of nitrogen and almost complete absence of other inclusions, Type IIa stones are prized for being transparent and colorless. For this reason, the CVD method is used to grow large amounts of such stones artificially.

Frankly, we do not yet fully understand what to do with this problem,” one sightholder said. “Our AMS checks 360 diamonds per hour and every hour we get about 5-10 “suspicious” stones. To confirm their natural origin, we have to send these diamonds for examination by more precise equipment. Such a check is worth about $ 20 for every stone, and in the case of melee additional checks of even a dozen of stones can make the purchase of an entire box loss-making. At the same time, we cannot sell them unchecked, because if someone from our customers will find a “synthetic” diamond by way of the same test, it will be useless to tell them stories about the existence of different types of rough. As a result, most of these stones are just stalled in our stock without movement.

In his turn, another sightholder said that his company used not only polished diamonds of its own make, but also bought diamond parcels from the market. “If this technological problem with the identification of Type IIa stones turned apparent to us, then most likely it has long been discovered by the companies producing synthetic diamonds. Where is the guarantee that these companies will not purposefully try to sell similar CVD diamonds to us? The market has long needed a machine like the AMS device to protect itself from synthetic diamonds, but it turns out that we have become less protected from synthetics with its introduction.

Such reaction gives rise to very sad reflections. Gemological experts are ready to listen to the arguments pointing to differences in the crystal lattice structure of diamonds. But the ultimate goal of creating machines to detect synthetics is to be able to use them in stores to give buyers an opportunity to be convinced that the stone he or she is purchasing is natural. And there, in the store, any story told by a sales assistant about nitrogen or boron inclusions is likely to make an average buyer think it is just another marketing ploy. Thus, it should be admitted that in this regard the problem of identifying synthetic stones is still far from being solved. The developers of such equipment will have to create a new class of portable devices combining several methods of identification used to test the origin of rough diamonds to make their application truly mainstream.

We see here yet another danger. If modern technologies identify natural diamonds as synthetic, this gives the producers of synthetic diamonds another opportunity to proudly say: “Look, our product does not differ from the natural. Even De Beers devices confirm this.

Source Rough&Polished