Glossary of Pearl Terminology

A working glossary of the terms used in pearl gemology, the pearl trade, and pearl jewelry retail. Definitions reflect the CIBJO Pearl Book 2024, GIA's 7 Pearl Value Factors paper, and standard trade usage where the two are consistent.

A

Akoya pearl. A saltwater cultured pearl produced by Pinctada fucata (also called P. fucata martensii), the Akoya oyster. Primarily produced in Japan, China, and Vietnam. Typical commercial size 6-8 mm; known for sharp, mirror-like luster.

A-D system. Tahitian producer grading scale: A is the highest grade, D the lowest. Not interchangeable with the AAA-A system used for South Sea, Akoya, and freshwater pearls — Tahitian A and AAA-A "A" mean very different things.

AAA-A system. Producer-defined grading scale used widely outside French Polynesia. AAA is the top grade, A the lowest jewelry grade. Not a CIBJO-mandated standard; calibration varies between producers.

Australian pearl. South Sea pearl produced in Australian waters from Pinctada maxima, predominantly the silver-lipped sub-variety. Australia accounts for roughly 60% of world South Sea output.

B

Baroque. A shape category for pearls that are highly asymmetric and irregular, lacking any rotational axis. Baroque South Sea and Tahitian pearls are prized for their individual character; they are usually priced below round pearls of the same species and size.

Bead nucleus. The small spherical core (commonly cut from Mississippi River mussel shell) implanted into a host oyster around which nacre is deposited to form a cultured pearl. Most saltwater cultured pearls have a bead nucleus; many freshwater pearls do not.

Bib necklace. A short, multi-strand necklace that drapes against the collarbone.

Blemish. A surface irregularity on a pearl — pit, bump, ridge, or wrinkle. Even AAA-grade pearls allow up to about 5% surface blemishes by area.

Bodycolor. The dominant colour of a pearl, as distinct from overtone and orient. South Sea bodycolors range across white, silver, champagne, and gold; Tahitian bodycolors include grey, black, and aubergine.

Bowing. A defect in which a strand of pearls bends or curves visibly when laid flat, usually caused by uneven drilling or unsymmetrical pearls.

Button. A shape category for pearls that are flattened on one or two sides, like a slightly squashed sphere. Button pearls are common in earring and ring settings where the flat side faces the metal.

C

Choker. A short necklace, typically 35-40 cm in length, that sits at the base of the neck.

Cultivation. The process of growing a cultured pearl, from oyster rearing through nucleation, growth, and harvest. Cultivation times range from 10-18 months for Akoya to 4-7 years for South Sea.

Cultured pearl. A pearl formed when a human technician implants a nucleus and/or tissue graft into a host mollusk. Virtually all commercial pearls sold today are cultured. Per US FTC and CIBJO rules, cultured pearls must be labeled "cultured" — the unqualified word "pearl" implies natural origin.

Circle (circled) pearl. A pearl with one or more concentric grooves or rings around its surface. Circled pearls occur naturally in Tahitian and South Sea production.

D

Drop. A pear- or teardrop-shaped pearl, with a wider lower end and a narrower upper end. Divided into "long drop" (more elongated) and "short drop" (more compact).

Drilling. The process of making a small hole through a pearl to allow stringing or post-setting. Half-drilled pearls (one hole, partial depth) are used for stud earrings and ring centres.

Disclosure (CIBJO/FTC). The requirement that any treatment beyond standard cleaning and matching — including bleaching, dyeing, irradiation, heating, coating, filling, and luster enhancement — be disclosed to the buyer at the point of sale.

E

Edison pearl. A trade name for large bead-nucleated freshwater pearls grown principally in China. Edison strains push freshwater pearl sizes into the 10-15 mm range, approaching saltwater proportions.

Excellent (luster grade). The top grade on GIA's five-step luster scale: reflections are bright and sharp.

F

Freshwater pearl. A cultured pearl produced by mussels of the genus Hyriopsis (primarily H. cumingii and H. schlegelii and their hybrids), cultivated predominantly in China. Many are nucleus-free, with the entire pearl composed of solid nacre.

G

GIA. Gemological Institute of America. Issues the Cultured Pearl Classification Report using the 7 Pearl Value Factors. Considered the industry's most authoritative independent grading authority.

Golden South Sea pearl. A South Sea pearl with natural golden body colour, produced by the gold-lipped sub-variety of Pinctada maxima. Predominantly farmed in Indonesia, the Philippines, and Myanmar.

Graduated strand. A necklace in which pearls increase in size toward the centre and decrease toward the ends.

H

Hand-knotted strand. A pearl necklace in which a knot is tied in the stringing thread between each pearl, so that if the thread breaks at most one pearl is lost. Standard construction for fine pearl jewelry.

Half-drilled. A pearl drilled with only one hole, partway through, for use in stud earrings, ring centres, and pendants.

I

Imitation pearl. A man-made bead designed to look like a pearl, typically of glass, plastic, or shell coated with a pearlescent lacquer. Must be labeled as imitation.

Indonesian pearl. A South Sea pearl produced in Indonesian waters; Indonesia is the world's largest producer of gold-lipped Pinctada maxima output.

Irradiation. A treatment used to darken pearl colour (commonly to produce "chocolate" pearls). Requires disclosure under CIBJO and FTC rules.

K

Keshi pearl. A pearl formed without a bead nucleus, typically when the implanted tissue graft generates a small all-nacre pearl as a by-product of the main nucleation. Often baroque in shape, with very high luster because the entire pearl is solid nacre. CIBJO categorizes keshi as a shape descriptor rather than a separate pearl type.

L

Luster. The intensity and sharpness of light reflected from a pearl's surface. GIA's five-step scale: Excellent, Very Good, Good, Fair, Poor. The single most important quality factor for most buyers.

M

Mabe pearl. A half-pearl (or "blister pearl") grown attached to the inside of an oyster shell rather than free in the tissue. Mabe pearls have a flat or near-flat back and are commonly used in earrings and rings. Sometimes called blister pearls in older literature.

Margaritifera. Pinctada margaritifera, the black-lipped pearl oyster that produces Tahitian pearls.

Matching. One of GIA's 7 Pearl Value Factors. The uniformity of size, shape, colour, luster, surface, and nacre quality across all pearls in a pair or strand.

Maxima. Pinctada maxima, the silver-lipped or gold-lipped pearl oyster that produces South Sea pearls. The largest pearl-producing oyster.

Maeshori. A Japanese luster-enhancement treatment historically applied to Akoya pearls. Requires disclosure.

Matinée. A necklace length, typically 50-60 cm.

N

Nacre. The composite organic-inorganic material that constitutes pearl: aragonite platelets bound by conchiolin protein. The thickness and quality of nacre determine durability, depth of luster, and surface character.

Nacre quality. One of GIA's 7 Pearl Value Factors. As of May 2025, GIA grades nacre on a five-step scale: Excellent, Very Good, Good, Fair, Poor.

Natural pearl. A pearl formed in the wild without human intervention. Extremely rare in the modern market; almost all pearls sold today are cultured.

Necklace lengths (standard). Collar: 30-33 cm. Choker: 35-41 cm. Princess: 43-48 cm. Matinée: 50-60 cm. Opera: 70-90 cm. Rope: 115+ cm.

Near-round. A shape category for pearls that are nearly spherical but with a small deviation from perfect roundness.

Nucleation. The surgical implantation of a bead nucleus and/or tissue graft into a host mollusk to initiate cultured-pearl growth.

O

Oriental pearl. Older trade term for natural pearls from the Persian Gulf, the Gulf of Mannar, and the South Pacific. Not in current technical use.

Orient. The subtle iridescent play of light visible on the surface of high-quality pearls, especially baroque shapes. Distinct from overtone and bodycolor.

Overtone. A secondary colour that appears as a sheen on top of the bodycolor. Common overtones: rose, silver, blue, green. Tahitian "peacock" is a combination overtone (green with rose).

Oyster. Common name for several genera of bivalve molluscs. Pearl-producing species include Pinctada fucata (Akoya), Pinctada margaritifera (Tahitian), and Pinctada maxima (South Sea). Freshwater pearl mussels are technically not oysters.

P

Paspaley. The largest Australian South Sea pearl producer. Uses a proprietary grading scale (Statement, Fine, Fashion, Foundation) and rates pearls on its internal "Five Virtues" (lustre, complexion, shape, colour, size).

Peacock. A multi-toned overtone characteristic of Tahitian pearls — typically a green base with rose and gold flashes. Does not occur as a natural overtone on South Sea pearls.

Pearl meat. The flesh of a pearl oyster after the pearl has been removed. Some species (notably Pinctada maxima) produce edible pearl meat as a by-product.

Princess (length). A necklace length of 43-48 cm, the most common single-strand length.

R

Round. The most symmetrical shape category and generally the most valuable for a given species, size, and colour.

Rope (length). A necklace length of 115 cm or more, the longest standard category.

S

Saltwater pearl. A pearl produced by a marine mollusk. The three principal saltwater varieties are Akoya, Tahitian, and South Sea.

Semi-baroque. A shape category for pearls with some symmetry but visible irregularity — partway between baroque and a clean drop, button, or oval.

Silver-lipped oyster. The sub-variety of Pinctada maxima that produces white, silver, and silver-blue South Sea pearls. Predominant in Australia.

South Sea pearl. A nacreous saltwater cultured pearl produced by Pinctada maxima. Produced in Australia, Indonesia, the Philippines, and Myanmar.

Surface. One of GIA's 7 Pearl Value Factors. The proportion of the pearl free of visible blemishes.

T

Tahitian pearl. A cultured pearl produced by Pinctada margaritifera in French Polynesia. Naturally dark body colours (grey, black, aubergine, green, blue) with peacock and rose overtones.

Tissue graft. A small piece of mantle tissue from a donor oyster, implanted along with the bead nucleus during nucleation. The graft is the biological source of the new pearl sac that lays down nacre.

Treatment. Any post-harvest modification beyond standard cleaning, drilling, polishing, buffing, peeling, and matching. Treatments including bleaching, dyeing, irradiation, heating, coating, and luster enhancement require disclosure under CIBJO and FTC rules.

U

Untreated. A pearl that has undergone no disclosure-required treatment. The label is defensible only with supplier attestation; cannot be applied generically.

V

Very Good (luster grade). The second-highest grade on GIA's five-step luster scale.

W

White South Sea pearl. A South Sea pearl with natural white body colour, produced by the silver-lipped sub-variety of Pinctada maxima. Predominantly Australian.

For deeper coverage of the variables defined above, see our pearl types comparison, the pearl grading guide, and the pearl care guide. To browse pearls organized by type, visit the South Sea pearls collection or the loose Tahitian pearls collection.