Letter grades are the seller's opinion. Here is the framework that actually decides what a pearl is worth.

Here is the thing most pearl sellers will not tell you: the A–AAA scale is not a regulated standard. Unlike diamonds, where GIA's 4Cs are used industry-wide, pearl letter grades are assigned by whoever is selling the pearl.

That does not make grading meaningless. It means you need to know what a reputable seller means by it — and what the actual gemological framework looks like.

What GIA actually uses: the 7 Pearl Value Factors

GIA does not grade pearls A, AA, or AAA. It classifies them using seven factors:

1. Size — measured in millimeters.
2. Shape — round, near-round, oval, drop, button, baroque.
3. Color — body color, overtone, and orient.
4. Luster — the sharpness of reflection.
5. Surface — the extent of visible blemishing.
6. Nacre — the thickness and quality of the layers themselves.
7. Matching — consistency across a pair or strand.

The A–AAA scale you see at retail is a trade convention layered on top of this. It is a shorthand, not a standard — and shorthand means different things in different hands.

So what does AAA mean?

Used honestly, AAA means very high luster, a surface that is clean at arm's length, excellent roundness, and consistent matching. That is how we use it.

Used loosely, it means whatever the seller wants. Some add AAAA or "gem" grades above it, which is marketing rather than measurement. This is why the factors below matter more than the letters.

The three that decide most of the value

Luster — the one that matters most

Luster is how sharply a pearl reflects light. Hold it near a window: on a high-luster pearl you should see a clear, almost mirror-like reflection with defined edges. On a poor pearl the reflection is soft and milky.

It cannot be faked or improved after harvest, and it is the single factor that makes a pearl look expensive or cheap.

Nacre — the one nobody asks about

Nacre is the substance the mollusk deposits, layer by layer. Luster is the visible result of it; nacre thickness is the underlying cause. Thin nacre over a large bead nucleus can look acceptable at first and dull within years — the pearl wears through.

This is the difference between a pearl that survives a generation and one that does not, and it is why time in the water matters. It is also the question that flushes out expertise fastest: ask a seller how thick the nacre is and listen to whether they can answer.

Matching — the labor nobody sees

On a strand or a pair of studs, consistency is everything. Twenty individually excellent pearls that do not match each other make a poor necklace. This is the most labor-intensive part of pearl work and the hardest to judge from a photograph.

The rest, briefly

Surface. Pearls are organic, so minor marks are normal. What matters is whether they are visible at arm's length. A blemish hidden near the drill hole is not a problem; visible pitting across the face is.

Shape. Round is rarest and priced accordingly. Near-round is often indistinguishable once worn. Baroque — deliberately irregular — is its own aesthetic, not a defect.

Color. Body color is the main hue. Overtone is the subtle secondary color floating over it — rose, silver, or cream on a white pearl. Overtone is what makes a pearl look alive rather than flat, and we go through it in detail in the overtones of Akoya pearls.

Size. Larger pearls cost more because they take longer to grow — but a 9mm pearl with dull luster is worth less than a 7mm with sharp luster. Size affects price; it does not determine quality.

What size to buy

How to judge a pearl yourself

1. Look at the reflection. Sharp and defined, or soft and chalky?
2. Hold it at arm's length. Can you see surface marks from there? If not, they do not matter.
3. Check the drill hole if you can. You can sometimes see the nacre layer against the bead nucleus — thin is a warning.
4. Roll it. Does it stay symmetrical?
5. On a strand, look down the line. Do the pearls match, or does your eye catch on one?
6. The tooth test. Real pearls feel faintly gritty against the edge of a tooth. Imitations feel glassy. Not conclusive on its own — use it alongside the rest.

One clarification worth making

A cultured pearl is a real pearl. It grows inside a living mollusk, of the same nacre, by the same process — with human help starting it. Natural pearls form without any human intervention and are today largely antique and rare. Imitation pearls are manufactured beads and are not pearls at all.

Every pearl we sell is a genuine cultured pearl. Anyone describing affordable pearls as "natural" is either confused or hoping you are. More on this in are cultured pearls real?

How we grade

We were among the first direct importers of both Akoya and freshwater pearl to major North American retailers, and three generations later we still select every pearl at the source — Akoya from Japan, Tahitian from French Polynesia, South Sea from Australia and Indonesia, freshwater from cultivated farms. The same people who choose the pearls set them at our New York atelier.

When we say AAA, we mean high luster, a clean surface at arm's length, excellent roundness, sound nacre, and hand-matching across every piece. If a pearl does not meet that, we do not sell it as AAA.

Questions about a particular piece? Reach us at sales@isaacwestman.com or 1-347-389-0766.

Next: which pearl is right for me, or how to care for pearls. Browse the pearl collection.

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ISAAC WESTMAN® · New York · Founded 1982