How to Read a Gemmological Certificate
The gemmological certificate is to a jewel what the registration document is to a car: the document that says what you are really buying. But you need to know how to read it. A practical guide, line by line.
Who Issues Certificates?
Independent laboratories, whose reputation is what gives the document its value. Among the most recognised: the LFG (Laboratoire Français de Gemmologie, in Paris), the American GIA, and the Swiss laboratories SSEF and Gübelin, world references for coloured stones, as well as GRS. A "certificate" produced by the seller themselves has no independent value whatsoever.
The Lines You Absolutely Must Read
- Identification / Species: the nature of the stone (corundum, beryl...) and its variety (sapphire, emerald...). This is the confirmation that it is indeed a natural stone;
- Weight, dimensions, cut: they must correspond exactly to the stone being shown to you;
- Colour: some laboratories award sought-after designations — "royal blue", "pigeon blood", "Padparadscha" — which strongly influence value;
- Treatment: THE crucial line. "No indication of heating" (or "no heat") means an unheated stone, rarer and more highly valued. For emeralds, the level of oiling ("minor", "moderate"...) is specified;
- Origin: Ceylon, Burma, Kashmir, Colombia... Geographical origin can multiply a stone's value, even though it remains an expert opinion.
The Traps to Know About
Check that the certificate number matches the stone (most laboratories offer online verification). Beware of certificates from unknown laboratories with vague wording, and remember that a certificate authenticates but does not value: it describes the stone; the market does the rest.
Our Practice
At Maxime Voillot Gems, our important stones come with certificates from recognised laboratories, and we can have any stone in our selection certified on request. Book an appointment to examine stones and certificates together, or browse our exceptional gems.
