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onyx marble[′än·iks ′mär·bəl]
(also alabaster, oriental alabaster, Mexican onyx), a dense, finely crystalline, semitransparent, lamellar, calcareous sinter rock. It consists primarily of calcite, sometimes together with aragonite. Marble onyx is formed from calcareous minerals deposited by hot mineral springs. The alternating irregular laminae, along with the varying coloration of the individual layers of white, yellow-pink, yellow-green, and brown tones, create a very attractive decorative pattern on polished surfaces of the rock. The thickness of the monochromatic and polychromatic bands varies from tenths of one millimeter to several centimeters. Marble onyx is used for mosaics and as facing. The best-known deposits of marble onyx in the USSR are in the Armenian SSR (Agamzalin) and the Turkmen SSR (Karliuk). There also are deposits in Algeria, the Arab Republic of Egypt, Argentina, Mexico, and other countries.