sedimentary

Bauxite

Bauxite (Al(OH)3, AlO(OH))

Hardness: 1-3 Mohs; Color: Brownish-red, yellow, or grey; Luster: Dull to earthy; Texture: Often pisolitic (pea-sized round grains) or massive earthy; Specific gravity: 2.0-2.5.

Hardness: 1-3 Mohs
Color: Brownish-red, yellow, or grey
Luster: Dull to earthy

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 1-3 Mohs; Color: Brownish-red, yellow, or grey; Luster: Dull to earthy; Texture: Often pisolitic (pea-sized round grains) or massive earthy; Specific gravity: 2.0-2.5.

Formation & geological history

Formed as a residual soil in tropical and subtropical regions through the intense chemical weathering of rocks high in aluminum silicate (laterization) over millions of years.

Uses & applications

The primary ore of aluminum used in metallurgy, chemicals, abrasives, and refractories.

Geological facts

Bauxite is not a mineral itself but a rock composed of hydrated aluminum oxide minerals like gibbsite, boehmite, and diaspore. The world's largest producers are Australia, Guinea, and Brazil.

Field identification & locations

Identified by its distinctive pea-like round concretions (pisolites), earthy smell when damp, and being relatively lightweight for its size. Often found as a thick surface soil layer in tropical climates.