Baroque: an irregularly shaped cultured pearl There are three basic degrees of irregularity: semi-baroque, baroque and heavy, or fishtail baroque.

Blister: a natural pearl usually caused by the chance intrusion of a parasite through the outer shell of a pearl-producing oyster. This name is sometimes, and erroneously, applied to certain cultured half pearls.

Cleanliness: absence of spots, cracks, or discoloration on a pearl's surface.

Color: an important criterion in pearl selection, and one influenced by the species of the mother oyster.

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

Cultured: a term for a pearl whose formation has been started by the insertion of a piece of mantle tissue with or \without a nucleus, into the mother oyster or mussel.

Imitation: having the appearance of natural or cultured pearls, but entirely man-made. See Mallorca.

Keshi: small pearls formed naturally in oysters or mollusks that produce cultured pearls. Often termed 11 seed" or " poppy' pearls.

Luster: the unique deep-seated glow, as opposed to surface shine, that distinguishes the pearl from all other gems. It is formed by the refraction of light through the crystals of the pearl nacre which, like prisms, create iridescent beams of color that seem to dance from the heart of the pearl. Thin coated or imitation pearls may reflect light to show a surface shine, but they do not absorb and refract rays of light.

Millimeter: the diameter measurement of the pearl. Approximately 1/25th of an inch.

Momme: Japanese weight measurement used for pearls. One momme is equivalent to 03.75 grams, or 1 8.75 carats.

Nacre: the substance which oysters secrete to form pearls. Made of microscopic crystals of calcium carbonate deposited in layers and bonded with an organic substance called conchiolin. Fine quality nacre gives the pearl its luster.

Nucleus: the stimulant placed in a pearl oyster, around which the oyster deposits nacre to form a pearl. The best nuclei are from the pig-toe clam found in the Tennessee, Wabash and Mississippi Rivers and exported to Japan.

Mother-of-pearl: the shiny interior of the upper and lower shells of certain oysters and mollusks, used to make decorative objects and buttons.

Natural: made or formed without the intervention of Man.

Orient: the delicate play of color on or just below the surface of a nacreous pearl.

Shape: one of the most important criteria in pearl selection. Common shapes for pearl strands are round, off-round (or near-round), semi-round, semi-baroque, baroque and heavy or fishtail baroque. Other shapes of loose pearls, mainly to be set into precious metal jewelry, may include buttons, drops, twins, crosses, doublets, triplets, sticks and dragons.

Size: an important criterion in the selection of pearls. Finished pearls are generally classified by either one or one-half millimeter gradations.

Graduated: necklace in which pearls of gradually increasing size are strung with the smallest pearls near the clasp and the largest at the center.

Uniform: necklace with nearly equalized pearls throughout.

Choker: a uniform pearl necklace that drops to just above the collarbone.

Princess: 1 8" in length.

Matinee: 20" to 24" in length.

Opera: 28" to 30" in length.

Bib: a pearl necklace of more than three strands.

Rope: a necklace 45" or more in length. Also called sautoir or lariat.