Pearl Types and Grades: Akoya, Freshwater, South Sea

Pearl listings throw around four names and one letter grade as if both were standardized. The names describe real differences in oyster species and growing conditions; the grade, mostly, describes the seller. Here is what is fixed and what is negotiable.

Four types, four animals

Akoya pearls come from small saltwater oysters (Pinctada fucata) farmed mainly in Japan and China. Typical sizes run 6 to 8 millimeters, in white with rose or silver overtones — the classic “pearl” of a graduated strand. Freshwater pearls are grown in mussels, overwhelmingly in China, in the widest range of shapes and sizes at the lowest prices. South Sea pearls, from the large Pinctada maxima oyster in Australia, Indonesia, and the Philippines, run 9 to 16 millimeters in white through gold. Tahitian pearls, from Pinctada margaritifera in French Polynesia, run roughly 8 to 14 millimeters in naturally dark grays and greens. Size, color, and price follow the species — a listing that says “akoya” but reads 12 millimeters is not using terms carefully.

Nacre is the part you cannot fake

Nacre is the layered material the mollusk deposits around the nucleus, and its thickness drives both luster and longevity. Bead-nucleated akoya pearls carry the thinnest coatings of the four — commonly a fraction of a millimeter — which is why cheap akoya can look chalky as the coating wears at the drill holes. Freshwater pearls, mostly tissue-nucleated, are nearly solid nacre. South Sea and Tahitian pearls typically carry coatings of a millimeter or more. Sellers rarely publish nacre thickness, so read it indirectly: a dull, eggshell-like surface or visible banding near the drill hole means the coating is thin.

What the grades actually mean

The AAA-to-A scale you see on tags is an industry convention — widely used, useful for comparing pearls within one seller’s catalog, and not an international standard that any body enforces. Two sellers’ “AA” pearls may not match. Luster is the factor worth obsessing over: it is the sharpness of light reflections off the nacre, and a high-luster 8-millimeter akoya will look better than a cloudy 10-millimeter one at any grade letter. Shape and surface get their own vocabulary: round, near-round, button, drop, and the free-form baroque; surface terms run from “clean” through blemish counts, spots, and pits. When you buy, compare within a seller and ask for their own grade definitions — the answer, or its absence, tells you plenty.

Care, briefly

Pearls are calcium carbonate with an organic binder — harder than they look, softer than they feel. Perfume, hairspray, and perspiration attack the nacre surface, so the routine is the reverse of most jewelry: pearls on last, pearls off first, then a wipe with a soft, barely damp cloth before the box. Skip ultrasonic cleaners entirely, and plan on restringing knotted strands every few years of regular wear. The same last-on, first-off logic protects plated metals too, which we covered in gold-filled versus vermeil labels. A small, deliberate jewelry rotation — the same idea behind a capsule wardrobe — keeps any strand from wearing out alone.