Pearl grading sounds like a science, and part of it is. But the heart of it is simpler and older: hold the pearl to the light, and look. This page explains both — the measures that matter, how the letter grades work, and how we apply them.
Last updated: 2026
The five measures
1. Lustre
The first thing the eye finds and the last thing it forgets. Lustre is the sharpness of the reflections on the pearl's surface — how crisply it returns the light you give it.
- Excellent: reflections are crisp, almost mirror-like; edges of light are sharp.
- Fine: bright reflections, slightly softened edges.
- Fair: hazy, diffuse light; the pearl glows rather than shines.
- Poor: dull, chalky; the surface reads flat.
Lustre comes from the nacre, which is why it tops every grader's list: it cannot be faked, coated or corrected.
2. Surface
Pearls are the skin of the sea, and their surfaces keep its records. Graders look at how much of the surface is clean:
- Clean: 95% or more free of marks — rare and prized.
- Lightly marked: small spots or ripples visible at arm's length.
- Moderately marked: visible blemishes, still sound in structure.
The test that matters: marks that are part of the pearl's character are fine; marks that threaten its structure — cracks, flakes, deep pits — are not, and we refuse them.
3. Nacre
The pearl's substance. Thick, well-formed nacre gives lasting lustre and a lifetime of wear; thin nacre dulls, and can chip or show the nucleus beneath. Nacre thickness is measured in millimetres and, more practically, read in the light: a pearl whose nacre is thin betrays itself with a faintly waxy glow and, at the extreme, a visible flicker of the nucleus.
4. Shape
Round is rarest; symmetry is difficult for an oyster. Graders move from round through near-round, oval, drop, button and baroque. Shape does not make a pearl good — it makes it itself. It does, however, move value: a perfectly round pearl of equal quality commands more than an irregular one.
5. Matching
For pairs and strands: how well the pearls agree in colour, lustre, size and surface. A strand is a chorus, not a soloist — the match is what makes it read as one piece of jewellery. The more pearls in the piece, the rarer the match, and the more of the price it explains.
How the letter grades work — and why to hold them lightly
You will see pearls sold as AAA, AA+, AA, A. The idea is simple: AAA is the top of the range — excellent lustre, clean surface, well-matched; A is commercial grade. But here is the honest part: there is no single international standard for these letters. One seller's AA is another's AAA. The grades are useful as a rough ladder, nothing more.
So we use them, and then we go further: every product page describes the piece in plain words — lustre, surface, size, colour — so you are never buying a letter. You are buying a pearl you can picture.
How we grade
- Every pearl is examined in daylight, against the five measures above.
- Pairs and strands are graded as a piece, not as individual pearls — the match is part of the grade.
- Anything structural — cracks, thin nacre, flakes — is refused outright, whatever its grade on paper.
- What we accept, we describe: the marks we can see, you should know about.
A note on perfection
A pearl without any mark at all is so rare that its price leaves the ordinary world. For everything else, the marks are not a secret — they are the signature. Two pearls have never been the same, and no two of our pieces will be. That is not the consolation prize of pearl buying; it is the whole point.