TERMS AND DEFINITIONS

Akoya pearl - Cultured saltwater pearls from the Akoya oyster (Pinctada fucata martensii), although called Japanese pearls, they can also be found in oysters outside Japan.

Baroque pearl - A pearl that is not round, free form in shape. 'Baroque' was originally a French adjective used to describe objects or pearls that were not classical or symmetrical in shape.

Black pearl - Natural dark color (not dyed) from the black-lip (Pinctada margaritifera) oyster found in the French Polynesia area. The term "black pearl" refers to any dark coloured pearl, dyed cultured pearl or natural color pearl.

Biwa pearl mussel - Hyriopsis schlegelii, the freshwater pearl mussel used for pearl culturing in Japan.  In Japanese, it is known as the 'Ikecho' mussel.  This species was endemic to Lake Biwa, but has been extinct since 1991 due to habitat alteration and over-collecting for pearl culturing.

Blemish - Tiny surface irregularities that mar the uniformity of the exterior of the pearl.

Black-lipped oyster - Pinctada margaritifera, used extensively for pearl culturing in French Polynesia.

Button pearl - A pearl in the shape of a button, disc or dome. The verticle axis of a Button pearl will always be shorter than its horizontal axis.

Circlé or circled pearl - A cultured pearl with one or more parallel concentric rings, bands or indented grooves around it's circumference.

Cultured pearls - A pearl produced by artificial, intentional insertion of a nucleus and grafting tissue, followed by maintaining the mollusc in culture until the pearl is harvested. 

Cultivation - Refers to the process whereby an oyster or mussel is seeded, tended and harvested to produce a cultured pearl.

Drop pearl - A pearl where the verticle axis is longer than its horizontal axis. Drop pearls are commonly in the shape of a teardrop, oval or egg.

Freshwater pearl - A pearl produced by various species of mussels in a lake, river, or pond usually farmed in China or Japan.

Gold-lipped oysterPinctada maxima is the largest species of pearl oyster, producing naturally golden pearls. Cultivated in Myanmar, Indonesia and the Philippines. As the name suggests the oysters inner shell edge is often golden yellow, and as a result it produces a golden range of South Sea pearls.

Imitation pearl - Man-made or machine made pearls. A bead (glass, plastic, or wax) that has been dipped in a resin containing powdered fish scales (essence d’orient), or (more recently) in another pearlescent coating.

Ikecho Mussel - Hyriopsis schlegelii, the mussel used for culturing Freshwater pearls in Japan. This species was endemic to Lake Biwa, but has been extinct since 1991 due to habitat alteration and over-collecting for pearl culturing.

Keshi - Tissue-nucleated pearls created during pearl culturing, when the implanted mantle tissue separates from the bead nucleus, or when no bead is grafted into the oyster, or when the oyster rejects the bead but the mantle bit remains. Keshi pearls are always irregular or baroque in shape.

Lustre - Lustre refers to the deep, lusterous glow of pearl. It is the result of light reflecting both from the surface of the pearl and light refracting within the layers of nacre within the pearl.

Mabé pearl - (pronounced mah-bay) A hemispherical pearl that develops whilst attached to the inner surface of a mollusc shell, also commonly referred to as a cultured blister pearl.

Mantle - A shell-producing organ of molluscs, lining the shell and secreting calcium carbonate.  Mantle tissue is used as the graft accompanying the bead nucleus for marine pearl nucleation; the mantle is the site of nucleation for most freshwater pearl culturing ventures.

Mikimoto, Kokichi (1858-1954) - Commonly referred to as the “father of modern pearl culturing,” he was the first to cultivate and continually improve the methods of pearl culturing. World famous for his brand of Mikimoto pearls.

Mikimoto pearls - Pearls produced and marketed by the Mikimoto Company. 

Mother-of-pearl - The smooth, hard, iridescent coating on the inner surface or lining of some species of molluscs, composed of microscopic crystals of aragonite (a form of calcium carbonate) deposited in thin layers with organic conchiolin;  scientifically known as nacre.

Mollusc - Mollusc are specific types of species of oysters and usually live in saltwater. Only a few species can produce pearls.

Nacre - (pronouced nay-ker) Nacre is the beautiful layers of crystalline material secreted by oysters and molluscs that form a pearl.

Natural pearl - Pearls produced naturally and without human intervention. Usually formed around an organic nucleus.

Non-nucleated pearls - A pearl formed by the insertion of tissue only. See Freshwater pearl.

Nucleus - A small object around which a pearl is formed. Frequently, a spherical piece of pearl mussel shell, or a small piece of mantle tissue.

Seed pearl - A minute pearl, defined as less than 2 millimeters in diameter.

South Sea pearls - Saltwater pearls cultivated in the large Pinctada maxima oyster in the area extending from the Philippines and Indonesia down to Australia and across to French Polynesia. 

Saltwater pearls - Pearls that are farmed in oceans, seas, gulfs, bays and salt lakes. The best-known example is the Akoya and South Sea Pearls.

Silver-lipped Pearl Oyster - Pinctada maxima, used extensively for pearl culturing in Australia, the Philippine Islands, Indonesia, and Myanmar.

Tahitian cultured pearl - The commercial name for a cultured pearl from the Black-lipped oyster, Pinctada margaritifera; also commonly referred to as a black pearl or (less frequently) a Black South Sea pearl.

Tissue-nucleated pearl - A cultured pearl produced by the insertion of the tissue graft only, without a shell bead; also called non-nucleated pearl, or seedless pearl.

Treated pearl - A pearl modified after harvest, usually with regard to colour, by bleaching, dying, irradiation, or chemical treatment, the modifications are collectively called treatments or enhancements.