GRA Certificate Numbers: What They Prove and What They Don't
A GRA card number is a reference, not a verification code. It tells you which run of cards this one came from and what the stone is meant to be — not whether the stone in your hand is the one the card was printed for.
What is actually printed on the card
A GRA card is a compact identification slip: material (moissanite), shape and cut, colour and clarity grades, dimensions in millimetres, weight in carats, and a card number. There is usually a QR code, a hologram, and a line of small print naming the issuing body.
That is the whole document — one card, roughly credit-card sized, in the same envelope as the stone. A diamond report is a multi-page document with a proportions diagram, a comments field and a searchable report number. The two are not the same class of object, and treating a GRA card as an IGI report leads to bad decisions.
The card is a batch document, not an individual one
Cards are printed in runs and matched to stones by size and weight, because moissanite is made in batches that are genuinely uniform: the material is grown to a fixed specification and cut to fixed dimensions. A run of 6.5 mm rounds will all be D colour and VVS1, so a card stating those grades is accurate for every stone in the run.
That is why the number does not work as a serial number. It identifies the batch and the specification, not one unique object. If two stones from the same run were swapped, both cards would still be correct about material and grades — only the millimetre measurement and the weight would change.
What the number can and cannot do
What it can do: give you a written specification to compare against the stone, and a paper trail if you resell or insure the piece. It also confirms on paper that you bought moissanite rather than cubic zirconia or glass — worth something, because that price difference is real.
What it cannot do: authenticate. There is no public database of GRA card numbers to search. You cannot type the number into a website and see the stone it belongs to. The number is not a check digit and it is not registered to a buyer. Any claim that a GRA number was "verified online" should be treated as marketing.
So how do you check the stone?
Two ways, and neither needs the card. The first is an electrical conductivity test: moissanite conducts heat like diamond, so an ordinary diamond tester reads it as diamond — the classic false positive. A moissanite tester, or a multi-tester that measures conductivity, separates the two in seconds. Any jeweller with a modern tester can do it while you wait.
The second is the caliper, and it is the check you can do yourself at the kitchen table.
The caliper check, step by step
A digital caliper costs less than a takeaway meal and reads to 0.01 mm. Measure across the girdle — the widest edge, not the table — at the widest point, then rotate 90 degrees and measure again. For a round, the two readings should sit within about 0.05 mm; more than 0.1 mm means the outline is slightly oval. For oval, pear and fancy shapes, measure length and width separately against the two figures on the card.
Allow plus or minus 0.1 mm. A stone listed at 6.50 mm that measures 6.44 mm is normal production variance. One that measures 5.90 mm is a different stone, or a different size, and the card does not belong to it.
Why the carat weight looks odd
Moissanite is less dense than diamond — silicon carbide, not carbon — so a stone of identical dimensions weighs close to ten per cent less. A 6.5 mm round diamond weighs about 1.00 ct; a 6.5 mm round moissanite of the same cut sits near 0.88–0.90 ct.
That is why cards quote a diamond-equivalent weight, and why a "one carat" moissanite may be printed as 0.90 ct while being sold as a one-carat equivalent. It is density showing up in the arithmetic, not a discrepancy. The millimetre figure is the honest one, because it is the same measurement for both materials.
When the card is missing
Loose moissanite is often sold without a card, especially in small sizes and in parcels, and that is normal in the trade. If the card matters, ask before you buy rather than after — a seller who supplies them routinely will say so.
| Field on the card | What it tells you | How you verify it |
| Material | Moissanite, not CZ | Jeweller's moissanite tester |
| Dimensions (mm) | Physical size | Caliper, within 0.1 mm |
| Weight (ct) | Mass or diamond equivalent | Compare against mm, not alone |
| Colour and clarity | D, VVS1 by specification | Eye and loupe; batch-printed |
| Shape and cut | Round brilliant, oval, etc. | Look at it |
| Card number | Batch reference | Nothing to look up |
What we make
Our moissanite is cut in our own factory in Wuzhou, Guangxi — we have been at it since 2008 — and each stone ships with a GRA card stating material, measurements, weight and colour at D/VVS1. Lab-grown diamond carries an IGI report instead, and we also work in lab-grown emerald, ruby and sapphire.
Settings are 925 silver or 9K, 14K and 18K gold. Pieces run from $17 to $2,020 with most around $98, shipping is free over $99 and $5.99 below it, and unworn pieces in original packaging can come back within 30 days — so if the caliper reads short, you are not stuck with it.
