Diamond Certification

When you buy a diamond its price depends amongst other things on the Four Cs - carat, clarity, colour and cut. The first of these - carat weight - is fairly straightforward to measure. However the other three are much more difficult for an untrained lay person to judge. So how do we know if we're paying a fair price for the stone? One answer is independent quality certification.

Dealers can have their diamonds certified by a reputable gemological institute who provide an appraisal of the stone's properties and quality. This information can then be shared with the buyer to reinforce confidence.

Certifying Bodies

There are three main bodies performing the most widely recognised diamond clarity and colour certification services today: the Gemological Institute of America (GIA), the American Gem Society (AGS) and the European Gemological Institute (EGL).

If you buy GIA, AGS or EGL certified diamonds then you can at least be sure that a trained gemologist has examined and rated the stone. So which is it best to have: GIA, AGS or EGL certification?

The full reports offered by each body differ slightly, but that's only likely to be of concern to an expert - most of us will just look at the headline grades. In the jewelry trade the GIA seems to be more popular, perhaps because its gradings are said to be somewhat stricter than the EGL. It's not unknown for the same stone to have an EGL rating one or two grades above its GIA rating, something you should bear in mind when comparing prices. AGS ratings also tend to be strict and they can include a cut rating for some standard diamond cuts.