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nacre(nā`kər), the iridescent substance that forms the lining of the shells of some fresh-water and some salt-water mollusks. Like the pearlpearl,
hard, rounded secretion formed inside the shell of certain mollusks, used as a gem. It is secreted by the epithelial cells of the mantle, a curtain of tissue between the shell and body mass, and is deposited in successive layers around an irritating object—usually a
..... Click the link for more information. it is a secretion of the mantle, composed of alternate layers of calcium carbonate and conchiolin. Among the chief sources are the pearl oyster, found in warm and tropical seas, chiefly in Asia; freshwater pearl mussels, which live in many rivers of the United States, Europe, and Asia; and the abalone of California, Japan, and other Pacific regions.
(also nacre), the internal layer of the shell of bivalve and gastropod mollusks; it is attached to the mantle, from which it is secreted. Mother-of-pearl consists of thin plates of aragonite (a variety of calcium carbonate) that are distributed parallel to the surface of the shell. It is distinguished by an iridescent sheen, which results from the interference of the light reflected by its surface. Mother-of-pearl is used for making ornaments, buttons, and other items.
Mother-of-pearl of saltwater origin is obtained from the shells of gastropods of the genera Turbo, Trochus, and Haliotis, as well as from the shells of bivalves of the genera Pteria and Mytilus. These mollusks inhabit the Persian Gulf, the Red Sea, and the waters off Australia and the Philippines. Mother-of-pearl of freshwater origin is obtained from the shells of bivalves of the family Unionidae. In the USSR, mother-of-pearl is obtained principally in the Bashkir ASSR, the Tatar ASSR, Moscow and Voronezh oblasts, the Ukrainian SSR, the Northern Caucasus, and the Far East. Pearls are a special variety of mother-of-pearl.
A. V. IVANOV