gypsum


gypsum
/jip"seuhm/, n.
a very common mineral, hydrated calcium sulfate, CaSO4·2H2O, occurring in crystals and in masses, soft enough to be scratched by the fingernail: used to make plaster of Paris, as an ornamental material, as a fertilizer, etc.
[1640-50; < L: chalk < Gk gýpsos chalk, gypsum]

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Common sulfate mineral, hydrated calcium sulfate (CaSO4·2H2O), of great commercial importance.

Deposits occur in many countries, but the U.S., Canada, France, Italy, and Britain are among the leading producers. Crude gypsum is used as a fluxing agent, soil conditioner, filler in paper and textiles, and retarder in portland cement. About three-fourths of the total production is calcined for use as plaster of paris and as building materials in plaster, board products, and tiles and blocks.

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 common sulfate mineral of great commercial importance, composed of hydrated calcium sulfate (CaSO4 · 2H2O). In well-developed crystals the mineral commonly has been called selenite. The fibrous massive variety has a silky lustre and is called satin spar; it is translucent and opalescent and is valued for ornaments and jewelry. The fine-grained massive variety called alabaster is carved and polished for statuary and ornamental use when pure and translucent. Gypsite is the earthy pulverulent variety.

      Gypsum occurs in extensive beds associated with other evaporite minerals (e.g., anhydrite and halite), particularly in Permian and Triassic sedimentary formations; it is deposited from ocean brine, followed by anhydrite and halite. It also occurs in considerable quantity in saline lakes and salt pans and is an important constituent of cap rock, an anhydrite-gypsum rock forming a covering on salt domes, as in Texas and Louisiana. Very commonly it is formed from the hydration of anhydrite by surface waters and groundwaters; thus, many gypsiferous strata grade downward into anhydrite rocks. This replacement causes a 30 percent to 50 percent volume increase and results in intense, tight folding of the remaining anhydrite layers. Gypsum also occurs disseminated in limestones, dolomitic limestones, and some shales.

      Gypsum deposits occur in many countries, but the United States, Canada, France, Italy, and Great Britain are among the leading producers. The largest gypsum crystal was found in the Braden mine in Chile and exceeds 3 metres (about 10 feet) in length and 0.4 metre (about 1.5 feet) in diameter. In the U.S., commercial sedimentary gypsum deposits occur in New York and Michigan; others of economic importance occur in Virginia, Ohio, Iowa, Kansas, Texas, Nevada, and southern California. In Canada, gypsum is produced for export in Nova Scotia and New Brunswick. In France, gypsum is common in the marls and clays of the Paris basin (hence the name plaster of paris), especially in Montmartre.

      Crude gypsum is used as a fluxing agent, fertilizer, filler in paper and textiles, and retarder in portland cement. About three-fourths of the total production is calcined for use as plaster of paris and as building materials in plaster, Keene's cement, board products, and tiles and blocks. Gypsum plaster is a white cementing material made by partial or complete dehydration of the mineral gypsum, commonly with special retarders or hardeners added. Applied in a plastic state (with water), it sets and hardens by chemical recombination of the gypsum with water.

      For especially hard finish plaster, the gypsum is completely dehydrated at a high temperature, and such chemicals as alkali sulfate, alum, or borax are added. Hair or fibre and lime or clay may be added to the plasters during manufacture. The plaster coats, except for some finish coats, are sanded. See also plaster of paris.

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Universalium. 2010.

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  • Gypsum — Gypsum, CO U.S. town in Colorado Population (2000): 3654 Housing Units (2000): 1210 Land area (2000): 3.680365 sq. miles (9.532101 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 3.680365 sq. miles (9.532101 sq …   StarDict's U.S. Gazetteer Places

  • Gypsum, CO — U.S. town in Colorado Population (2000): 3654 Housing Units (2000): 1210 Land area (2000): 3.680365 sq. miles (9.532101 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 3.680365 sq. miles (9.532101 sq. km) FIPS… …   StarDict's U.S. Gazetteer Places

  • Gypsum, KS — U.S. city in Kansas Population (2000): 414 Housing Units (2000): 179 Land area (2000): 0.432824 sq. miles (1.121009 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 0.432824 sq. miles (1.121009 sq. km) FIPS code …   StarDict's U.S. Gazetteer Places

  • Gypsum — Gyp sum (j[i^]p s[u^]m), n. [L. gypsum, Gr. gy psos; cf. Ar. jibs plaster, mortar, Per. jabs[imac]n lime.] (Min.) A mineral consisting of the hydrous sulphate of lime (calcium). When calcined, it forms plaster of Paris. {Selenite} is a… …   The Collaborative International Dictionary of English

  • GYPSUM — Graec. γυψος, quasi γῆ ἑψηθεῖσα, terra cocta, cognata calci res est, Plin. l. 36. c. 24. Plura eius genera, nam et e lapide coquitur, ut in Syria ac Thuriis: et e terra foditur, ut in Cypro ac Perrhpebis: e summa tellure et Tymphaicum est. Qui… …   Hofmann J. Lexicon universale

  • gypsum — substance (hydrated calcium sulphate) used in making plaster, late 14c., from L. gypsum, from Gk. gypsos chalk, according to Klein, perhaps of Semitic origin (Cf. Arabic jibs, Hebrew gephes plaster ) …   Etymology dictionary

  • gypsum — [jip′səm] n. [ME < L < Gr gypsos, chalk, gypsum < Sem] a very soft, monoclinic mineral, CaSO4·2H2O, commonly found with other evaporites in sedimentary rock and used to make plaster of Paris and cement; hydrous calcium sulfate: see MOHS… …   English World dictionary

  • gypsum — ► NOUN ▪ a soft white or grey mineral used to make plaster of Paris and in the building industry. ORIGIN Latin, from Greek gupsos chalk …   English terms dictionary

  • Gypsum — Infobox mineral name = Gypsum category = Mineral boxwidth = boxbgcolor = caption = Desert rose, 10 cm long formula = Calcium Sulfate CaSO4·2H2O molweight = color = White to grey, pinkish red habit = Massive, flat. Elongated and generally… …   Wikipedia


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