lateritic

Lateritic refers to materials formed by extensive tropical weathering, yielding laterite, a highly altered rock or soil that is rich in iron and aluminum oxides and hydroxides. Laterite can occur as a hard, cemented rind on bedrock or as a softer, clay-rich soil horizon. The term is often used for both the cemented crust and the weathered material beneath it.

Formation of laterite occurs under hot, humid tropical climates with abundant rainfall. intense chemical weathering leaches silica, mobile alkalis, and alkaline earths from the parent rock, concentrating iron and aluminum oxides near the surface. The resulting profile typically features a ferruginous, iron-rich layer at or near the surface and a clay-rich, weathered horizon beneath. The color ranges from red to yellow-brown due to iron oxides, and the physical properties range from friable to hard and brick-like when cemented.

Composition commonly includes iron oxides such as goethite and hematite, aluminum oxides and hydroxides such as gibbsite and boehmite, and clay minerals like kaolinite. Silica is depleted relative to the parent rock. The exact makeup varies with climate, parent rock, and drainage, leading to a spectrum from weathered soils to dense, lateritic crusts.

Types and occurrence: Laterite forms in tropical regions worldwide, including Africa, Asia, Australia, and the Americas. It can cap bedrock, form saprolite- or soil horizons, and, in certain settings, host economically important ore deposits such as nickel laterites or bauxite, the latter being a primary source of aluminum.

Uses and significance: Lateritic materials are used locally as construction material and soil cover. Economically, nickel and aluminum sources arising from lateritic weathering underpin mining and processing in various regions.