When you receive a diamond certificate, you are receiving a document written by one of a handful of gemological laboratories. Understanding who wrote it - and what that means - is part of understanding what you are buying.
What a certificate actually is
A diamond certificate, also called a grading report, is an independent assessment of a stone's characteristics. It does not set a price. It does not tell you what the diamond is worth. It records, to the best of the issuing laboratory's ability, the physical attributes of the stone: carat weight, colour grade, clarity grade, cut grade, and a range of additional measurements.
The certificate is issued by a laboratory that has examined the stone. It is as reliable as the laboratory that wrote it.
The two names you will encounter most
GIA - the Gemological Institute of America - was founded in 1931. It created the 4Cs grading system that the entire industry now uses. For natural diamonds, it is widely regarded as the most rigorous grading standard in the world. GIA reports are conservative: when GIA grades a stone, the consensus is that it is graded to a strict and consistent standard.
IGI - the International Gemological Institute - was founded in 1975, with laboratories across Antwerp, New York, Mumbai, Hong Kong, and elsewhere. It has become the dominant certification body for lab-grown diamonds. When the lab-grown market expanded, IGI was faster to develop the grading infrastructure for it, and today a large proportion of lab-grown diamonds globally carry IGI certification.
How they compare
Both GIA and IGI use the same 4Cs framework. Both employ trained gemologists. Both are internationally recognised and accepted by retailers, insurers, and the secondary market.
There are two practical differences.
- Grading conservatism: GIA is generally considered the stricter grader of the two for natural diamonds. For the consumer, this means that when comparing stones certified by different laboratories, like-for-like grade comparison is not always straightforward - a stone graded VS1 by one lab might be graded VS2 by the other.
- Market position in lab-grown: IGI has significantly higher volume and experience in lab-grown grading than GIA. It is the market standard for this category, and HEIREST uses IGI certification for this reason - it is the most widely understood and recognised certificate for the stones we source.
What the certificate does not tell you
A grading report is a snapshot of a stone at a point in time, under laboratory conditions. It does not assess beauty. It does not tell you how a stone will perform in a specific setting, in a specific light, on a specific hand.
Two stones with identical certificate grades can look very different in person. Cut quality - which the certificate does document - is the single most important factor in visual performance, but even within an Excellent or Ideal grade there is variation.
A grading report is a starting point. A well-specified stone is the outcome.
HEIREST and IGI
Every HEIREST diamond of one carat or greater is accompanied by an IGI certificate, included with your piece. For stones below one carat, specifications are documented in your HEIREST Statement of Authentication. IGI certification is available on request for coloured stones.
The certificate does not change what the stone is. It confirms it.
