Almost every moissanite ring sold online in the UK and EU arrives with a certificate. Many of them mean far less than the buyer thinks. The gap between a GRA card and an IGI report is wide enough to change the price you should be willing to pay, so it is worth ten minutes of your time.
What GRA is — and what it is not
GRA stands for Gemological Research Association. It is not a laboratory that inspects the individual stone. There is no GIA-style master stone comparison, no measured table percentage, no crown angle, no plot of inclusions on the back of the card.
What you get is a printed card, usually with a hologram and a certificate number, stating the stone type, weight, shape and a grade band. The cards are issued in bulk against production runs rather than against a specific stone under a microscope. That is why you can find thousands of moissanite rings for sale whose GRA cards all list the same 6.5mm, 1ct, D colour specification. They are not all wrong. They are all generic.
What IGI does differently
IGI — the International Gemological Institute — is a real grading laboratory. It weighs the stone on a calibrated balance, measures its dimensions in millimetres, describes the cut, colour and clarity, and prints a report tied to that specific stone. You can look the report number up on IGI's own website and see whether it matches what you were sold.
IGI also grades lab-grown diamonds, and increasingly moissanite, with a turnaround measured in days to a few weeks rather than the months a full GIA submission can take. Expect a fee in the region of €60 to €120 per stone for a full report on a single item. That number is why cheap mass-market moissanite does not carry one.
What a certificate will tell you
- Species. A real report states moissanite, or silicon carbide, explicitly. If it says diamond, you have a diamond report, not a moissanite one.
- Weight. In carats or grams, measured rather than assumed.
- Dimensions. Width, length and depth in millimetres. This is the single most useful line on the page.
- Shape and cut style. Round brilliant, oval, radiant, emerald, and the facet arrangement.
- Colour and clarity bands. On an IGI report these are graded; on a GRA card they are usually a house band.
- Report number. Honest sellers quote it in the listing so you can verify it before you pay.
What no certificate will tell you
It will not tell you the cut quality in any meaningful sense. Neither GRA cards nor the standard IGI moissanite report give you the table percentage, crown angle or pavilion depth that you would need to judge light performance. Those numbers exist, they are just not on the document.
It will not tell you how the stone looks. A certificate cannot describe a bow-tie across an oval or a dark patch under the table.
And it will not tell you the stone in your hand is the stone on the paper. Only verification does that.
How to verify a certificate in five minutes
- Find the report or certificate number in the listing. If it is not published, ask for it before ordering.
- Look it up on the issuing lab's own website. For IGI, use the IGI checker. A GRA number that cannot be looked up anywhere official tells you what you need to know.
- Compare the millimetres on the report with the millimetres in the listing. Mismatches here are common and they matter.
- Check the weight against the millimetre table. A 6.5mm round that is listed as 1.2ct is not a 6.5mm round.
- Test the stone if you can. A thermal tester will separate moissanite from diamond instantly, and a loupe will show the doubled facet lines that double refraction creates.
Common mis-selling to watch for
The most frequent is quoting the certificate as though it were a diamond grading report. "GRA certified D colour" invites the buyer to hear "GIA graded D colour", and those are not remotely the same claim.
Second is the diamond tester. Many cheap testers read moissanite as diamond, because both conduct heat similarly. Sellers who lead with "tested as diamond" are either using a tester that cannot distinguish them or know it and are relying on you not knowing. A multi-tester with a moissanite setting is a different instrument and it will say moissanite.
Third is the carat figure. As covered in our guide to millimetres, a moissanite sold as 1ct may weigh around 0.88ct on a scale, because the number is a diamond-equivalent size label. Not dishonest if disclosed, misleading if it is not.
Fourth is a certificate number that does not match the stone actually shipped. This is why you photograph the certificate on arrival and check the millimetres against your own ruler.
What to do about it
If you are buying a small moissanite ring as a piece of jewellery to enjoy, a GRA card is acceptable. It costs the seller almost nothing and it is not evidence of anything.
If you are spending real money — anything over roughly €600, or any stone at 8mm and above — ask whether the stone can be submitted to IGI, and expect to pay for it. On a large stone, an independent report is a few per cent of the purchase price and it is the only document in the transaction that means anything in a dispute.
Read our guide to moissanite resale and insurance for how insurers treat these documents.