bauxite

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bauxite A mixture of three hydrates of alumina, mainly gibbsite, and also diaspore and boehmite, and containing impurities of iron, phosphorus, and titanium; colour is variable from dirty white through grey, yellow, brown, and red; sp. gr. 2.0–2.55; hardness 1–3; it can be compact, earthy, concretionary (see CONCRETION), pisolitic, or oolitic. Bauxite results from the tropical weathering of aluminium silicate rocks under good surface drainage to yield clay minerals which are subsequently desilicated. Minerals associated with the alumina hydrates in bauxites and laterites (ferruginous bauxites) include goethite and lepidocrocite, hematite, and the clay minerals kaolinite and halloysite. Bauxite is the main ore of aluminium and to be commercially exploited should contain more than 25–30% aluminium oxide. The main constraint is the amount of available alumina which can be extracted by the Bayer or similar process. It is named after Les Baux de Provence, in southern France; the major producers are Australia and Brazil.

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bauxite (bôk´sīt, bŏk´–), mixture of hydrated aluminum oxides usually containing oxides of iron and silicon in varying quantities. A noncrystalline substance formerly thought to be a mineral, bauxite is claylike and earthy and ranges in color from white to deep brown or red according to the nature and quantity of its components. Bauxite occurs characteristically in pisolitic form, i.e., composed of small, round concretions. Its composition varies, alumina constituting from about 50% to about 70%. First discovered in Les Baux, France, bauxite is widely distributed, with important deposits occurring in Africa, South America, Russia, the West Indies, and the United States (Alabama, Arkansas, and Georgia). It is the chief source of aluminum and of its compounds, including alumina, alums, and alundum. It is used in the preparation of abrasives and as a refractory for spark plugs and furnace linings.

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baux·ite / ˈbôksīt/ • n. an amorphous clayey rock that is the chief commercial ore of aluminum. It consists largely of hydrated alumina with variable proportions of iron oxides. DERIVATIVES: baux·it·ic / ˌbôkˈsitik/ adj.

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bauxite XIX. — Fr., f. Les Baux, near Arles, France; see -ITE.

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bauxite Rock from which most aluminium is extracted. Bauxite is a mixture of several minerals, such as diaspore, gibbsite, boehmite and iron. It is formed by prolonged weathering and leaching of rocks containing aluminium silicates.