The Truth About Diamond Certification

Diamond certificates

Consumers have access to huge amounts of information about the ‘4C’s, the criteria by which diamonds are assessed. But there is far less discussion about the grading laboratories themselves, and the value of the certificates they issue. So as a layperson with a limited knowledge of diamonds, what do you need to know before you make a big investment in a diamond engagement ring.

The first thing to bear in mind is that a certificate is the expression of a gemologist’s opinion - it doesn’t represent a hard scientific fact. Judgements can and do vary between laboratories, and even within a particular laboratory we can’t expect to see absolute consistency. If you were to put two diamonds with nearly matching certificates side by side, it wouldn’t be unusual to find that one stone was clearly more attractive than the other. The lesson from this is that wherever possible the consumer should view the diamond in person before making a decision. Certification is important, but it’s only the first part of a ‘double tick’ system - if the diamond doesn’t look how she hoped it would, there is no certificate in the world that will redeem the situation.

The next consideration is the fact that not all laboratories are equally credible. The Gemological Institute of America (GIA) and the American Gemological Society (AGS) are known to have the most rigorous standards, while other laboratories are comparatively more lenient in their assessments. In 2013, the Rapaport Diamond Trading Network conducted an experiment to demonstrate this. Ten diamonds of various sizes and qualities were sent to different laboratories for assessment. As expected, the results showed that laboratories such as the International Gemological Institute (IGI) and HRD Antwerp tend to grade stones more leniently than GIA.

Does this mean that we should rule out taking a diamond with a certificate from IGI or HRD? Not necessarily. The key is that it shouldn’t be priced the same as a diamond with the same grades from GIA. If the price is discounted sufficiently, there is no reason reject it. A degree of knowledge is essential - the consumer needs to be aware of the comparative values of these different certificates to ensure they get a fair deal.

One laboratory that should certainly be avoided is EGL (European Gemological Laboratory). EGL-graded diamonds have recently been banned by the industry’s two major online trading platforms (Polygon Trading Network and Rapnet). This development followed the news in 2014 that customers were taking legal action against Genesis Diamonds, a retailer in Nashville. The claim was that by supplying diamonds graded at EGL, Genesis was essentially misrepresenting their stones. Depending on the outcome of the case, it’s quite possible that many jewellers will be hit with a deluge of claims for refunds, or at the very least for retrospective discounts.

Another minefield is the issue of uncertified diamonds. Above about 0.3ct, most diamonds available to the consumer will come with some form of laboratory certification. The supplier will factor the cost of this into the pricing of the diamond. Below about 0.3ct, this tends not to happen - the premium the supplier can charge for the certificate is not enough to justify the cost of it.

What should we make then of diamonds above 0.3ct that haven’t been certified? It’s possible that the explanation is perfectly innocent. For example, the stones may have been newly cut, and then needed before there was time to certify them. However, it is also possible that the supplier is worried that certification will reveal some undesirable aspect to the diamond, and is trying to pass them off as something they are not. For example, it’s very unusual to see a round brilliant cut diamond that has been graded ‘Poor’ for Cut. Suppliers know that far from helping them sell the diamond, a certificate like this will have the exact opposite effect. So what happens to poorly-cut diamonds? Clearly the vast majority of them get sold uncertified. If you are offered an uncertified diamond, the retailer should certainly have no objection if you offer to pay for it to be certified before making a decision.

Consumers should be particularly wary of retailers who exclusively sell uncertified (or ‘self-certified’) diamonds. For the reasons mentioned above, it may sometimes be necessary to handle uncertified stones, but a blanket policy of this type should always ring alarm bells - if a retailer chooses to exclusively offer diamonds without third-party assurances, then there is probably a good reason for this. Claims that ‘we only choose the finest diamonds, we don’t need independent certification’ should be dismissed for what they are. All jewellers take care over the diamonds they select, but this doesn’t undermine the value of having an independent expert assess your stone.

Talk to an Expert

Talk to an expert

020 7499 2012

Appointment calendar Contact us