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a metamorphic rock, composed chiefly of clinopy-roxene and garnet. The clinopyroxene (omphacite) is a mixture of diopside, hedenbergite, and jadeite components; the mixed-composition garnet contains pyrope and almandine, as well as variable amounts of grossularite and andradite. Eclogite varieties with significant amounts of grossularite and disthene (kyanite) are called grospydites.
Various types of eclogite are distinguished according to the content of secondary minerals, including amphibole, enstatite, olivine, plagioclase, kyanite (disthene), corundum, rutile, graphite, and diamond-containing eclogites. Three types are distinguished on the basis of geological conditions of occurrence: the eclogites of the metamorphic zone, which are associated with glaucophane schists and alpine-type hyperbasites; the eclogites of granulite, gneiss, and amphibolite metamorphic complexes; and eclogites that form inclusions (xenoliths) in kimberlites and alkali basaltoids. The first two are formed within the crust; the last is of mantle origin. Deposits of rutile are associated with eclogite, and diamonds are found among the most deep-seated eclogites in kimberlite pipes.
A. A. MARAKUSHEV