01Decisive
The report verifies on IGI's own service
Free, public, and returns the grades issued against the number. A number that does not resolve, or grades that differ from the printed ones, is decisive.
Lovenhall Diamond
Verify a IGI report
The laboratory that grades most of the world's lab-grown diamonds, with its own free verification service.
Founded 1975Antwerp4 weighted checks
The International Gemological Institute grades a very large share of the world's laboratory-grown diamonds and a substantial volume of natural stones, particularly in jewellery sold at retail. Its reports are widely accepted and, like GIA's, verifiable online for free.
The thing to understand about IGI is not authenticity but calibration. IGI's colour and clarity grading is commonly regarded in the trade as running a grade or so softer than GIA's, so an IGI VS1 G and a GIA VS1 G are not necessarily the same stone. That is why IGI-graded stones typically trade below GIA-graded equivalents at the same stated grades.
Verification works identically: report number, online lookup, then match the inscription and the measurements to the stone.
The maker's own mark
Verifying an IGI report
IGI reports carry a number that can be checked on the institute's own free verification service, which returns the grades issued against it. Compare every field against the printed document.
IGI laser-inscribes report numbers on the girdle of a great many graded stones, particularly laboratory-grown ones where the inscription commonly also states that the stone is laboratory-grown. That inscription is required disclosure in several markets and is the check that ties the report to the stone.
IGI reports state origin explicitly — natural or laboratory-grown — and for grown stones the growth method where determined. Reading that field is the single most important thing on the document for a buyer.
The checks
How IGI is read
Ordered by how much each one settles. The decisive checks are the ones worth your first five minutes; the supporting ones only matter once those are clean.
02Decisive
The origin field, read carefully
IGI reports state whether a stone is natural or laboratory-grown. Grown stones are commonly inscribed as such on the girdle. A seller describing an IGI-graded stone as natural where the report says otherwise is misrepresenting it, and this is the commonest problem in the category by a wide margin.
03Strong
Inscription matches the report number
Have a jeweller read the girdle under magnification. The inscription should carry the report number and, on grown stones, the laboratory-grown designation.
04Strong
Measurements agree with the stone
Dimensions in millimetres, table and depth percentages. A mismatch means the report belongs to a different stone.
Where a fake gives itself up
What a counterfeit pays for, and what it skips
Outright forgery of IGI reports exists and is defeated by verification. The dominant problem in this category is different: laboratory-grown stones sold as natural, with a genuine IGI report whose origin field the buyer did not read.
Because grown diamonds are chemically and optically identical to mined ones and cost a fraction as much, this is the single most expensive mistake a buyer can make, and it does not require anyone to forge anything.
The failures worth looking for first
- A report number that does not verify.
- An origin field the seller has not mentioned.
- A girdle inscription reading laboratory-grown on a stone sold as natural.
- An IGI grade compared directly against a GIA grade as though equivalent.
Questions we are asked
- How do I verify an IGI certificate?
- Enter the report number on IGI's free online verification service and compare every grade against the printed report, then have a jeweller confirm the inscription on the girdle matches the number.
- Is IGI as strict as GIA?
- Generally regarded in the trade as somewhat softer on colour and clarity, which is why IGI-graded stones typically trade below GIA-graded equivalents at the same stated grades. It is a calibration difference, not an authenticity one.
- Does IGI grade lab-grown diamonds?
- Yes, and it grades a very large share of them. IGI reports state origin explicitly and grown stones are commonly inscribed as laboratory-grown on the girdle.
The other laboratories and houses the room reads
Free tools of the room
Lovenhall DiamondRead the stone itself
The checks tell you how it was made. The instrument tells you what it appears to be, and roughly what its kind fetches.
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