Mabe pearl: Assembled blister pearl. The blister pearl is cut from the shell, the dome is removed and the interior filled with epoxy. The back is finished with a mother of pearl cap.

Mise-Nishikawa method: Patented by K. Mikomoto in 1916, the method of culturing pearls with a bead-nucleus and donor mantle tissue.

Mikimoto, Kokichi: The first to market whole cultured akoya pearls.

Millimeter: The unit of measure used to determine the diameter of a pearl.

Momme: Ancient Japanese unit of measure now used exclusively for pearls. One momme is equivalent to 3.75 grams.

Mother of Pearl: The hypostracum, prismatic inner-shell layer of a bivalve mollusk composed of aragonite crystals.

Nacre: The substance secreted by the epithelial cells which forms the pearl.

Natural pearl: A pearl grown without human intervention.

Nucleus: The bead inserted into the gonad of pearl mollusks to create a cultured pearl.

Opera length: Pearl strand of 35 to 36 inches (90 centimeters).

Orient: The diffraction of light from the linear layers of nacre creating a prismatic effect.

Oriental pearl: A natural, marine pearl.

Peacock color: Dark green color with varied overtones of red and purple found primarily in natural color black South Sea pearls.

Peeling: Removing the outer layer of a pearl in the hope of finding a finer pearl layer.

Pinctada fucata martensii: Used to culture akoya pearls.

Pinctada maxima: Used to culture South Sea pearls.

Pinctada margaritifera: Used to culture Tahitian pearls.

Pteria sterna: The rainbow-lip mollusk used to culture Cortez pearls™.

Pteria penguin: Also known as the "mabe-gai" used to culture mabe pearls.

Poe Rava: See peacock color.

Princess length: Pearl strand of 17 to 18 inches (45 centimeters).

Queens length: Pearl strand of 31 to 32 inches (80 centimeters).

Quahog: Cherrystone clam which produces small, natural pearls that range from white to lavender, to deep purple.

Sautoir: Pearl strand longer than 40 inches (100 centimeters).

Saville-Kent, William: British expatriate marine biologist who is believed to have first discovered what is now known as the Mise-Nishikawa method of pearl culturing.

Seed pearl: Tiny pearl, usually smaller than 2 mm in diameter.

South Sea Pearl: Produced by the Pinctada maxima in Australia, Indonesia, the Philippines, Myanmar (Burma), Malaysia and Vietnam.

Tahitian Pearl: Produced by the Pinctada margaritifera mollusk (Black-lip oyster) in French Polynesia.

Taverneir's rule: Developed by Jean Baptiste Tavernier, a method for evaluating natural pearls by multiplying grain weight by factors of 1-20 based on four quality attributes.

Tridacna gigas: Giant clam: producing non-nacreous, calcareous concretions known as giant clam pearls.

X-Radiographs: Used to test for imitation, cultured, and natural pearls.

Zuchtperlen: Early German translation of cultured pearls.

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