Laterite

Laterite is a type of soil produced by intense, prolonged weathering, usually in tropical climates. Abundant oxygen , water , and warmth leach most water-soluble minerals from particles of parent rock and leave a nonsoluble residue enriched in hydroxides of aluminum , iron , magnesium, nickel, and titanium. Laterites high in specific metals are often stripmined as ores.

Laterite rich in aluminum are termed aluminous laterite or bauxite. Aluminous laterite is formed from clay minerals such as kaolinite (Al₄[Si₄O₁₀][OH]₈) by the leaching of silica (SiO₂). The residue left by the leaching of silica, aluminum hydroxide (Al[OH]₃), is termed gibbsite. Gibbsite's dehydrated forms, diaspore and bohemite (both HAlO₂), are also common components of aluminous laterite. Aluminous laterite is the world's primary source of aluminum.

Laterite descended from basalt is rich in iron and nickel and is termed ferruginous laterite. Laterite formed from rocks particularly rich in nickel may contain a high percentage of the mineral garnierite ([NiMg]₆Si₄O₁₀[OH]₈). A continuum of mixed laterites exists between the aluminous and ferruginous extremes. Nickeliferous laterites are an important commercial source of nickel.

See also Soil and soil horizons; Weathering and weathering series

lat·er·ite / ˈlatəˌrīt/ • n. a reddish clayey material, hard when dry, forming a topsoil in some tropical or subtropical regions and sometimes used for building. ∎ Geol. a clayey soil horizon rich in iron and aluminum oxides, formed by weathering of igneous rocks in moist warm climates.DERIVATIVES: lat·er·it·ic / ˌlatəˈritik/ adj.

laterite Weathering product of rock, composed mainly of hydrated iron and aluminium oxides and hydroxides, and clay minerals, but also containing some silica. It is related to bauxites and is formed in humid, tropical settings by the weathering of such rocks as basalts. See also PLINTHITE.

laterite. Red, porous, ferruginous (i.e. containing iron) rock, found in India and parts of South-East Asia. It is easy to cut when first excavated, but soon becomes extremely hard on exposure to air. It was used in blocks for walls, with no mortar, but surfaces had to be clad with softer stone or plastered if decoration was required as it was too hard to carve.

Bibliography

Geographical Review, xxxi (1941), 177–202;
W. Papworth (1852)

laterite A weathering product of rock, composed mainly of hydrated iron and aluminium oxides, hydroxides, and clay minerals, but also containing some silica. It is related to bauxites and is formed in humid, tropical settings by the weathering of such rocks as basalts. After exposure at the surface it can become a hard, impermeable layer and it has been used as a building material.