sedimentary
Bauxite
Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))
Hardness: 1-3 Mohs; Color: reddish-brown, white, tan, or grayish; Luster: dull to earthy; Structure: pisolitic (pea-like) or earthy; Cleavage: none; Specific Gravity: 2.0-2.5
- Hardness
- 1-3 Mohs
- Color
- reddish-brown, white, tan, or grayish
- Luster
- dull to earthy
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Physical properties
Hardness: 1-3 Mohs; Color: reddish-brown, white, tan, or grayish; Luster: dull to earthy; Structure: pisolitic (pea-like) or earthy; Cleavage: none; Specific Gravity: 2.0-2.5
Formation & geological history
Formed as a residual soil in tropical and subtropical regions through the intense chemical weathering (lateralization) of silicate rocks like granite, basalt, or shale. Typically Cenozoic to recent in age.
Uses & applications
Primary ore of aluminum; used in the manufacture of abrasives, cement, chemicals, and refractory materials.
Geological facts
Bauxite is not a mineral in the strict sense but a mixture of hydrous aluminum oxides. It was first discovered in 1821 by Pierre Berthier near the village of Les Baux in France.
Field identification & locations
Identify by its distinctive pisolitic (round, pea-sized) texture and clay-like or earthy appearance. It is commonly found in tropical belts such as Guinea, Australia, Brazil, and Jamaica. Collectors look for well-defined pisolites.
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