sedimentary
Bauxite
Al2O3·2H2O (principally composed of gibbsite, boehmite, and diaspore)
Hardness: 1-3 on Mohs scale; Color: Reddish-brown, tan, or yellow; Luster: Dull to earthy; Crystal structure: Amorphous or microcrystalline; Cleavage: None; Pisolitic/Oolitic texture (pea-sized round inclusions).
- Hardness
- 1-3 on Mohs scale
- Color
- Reddish-brown, tan, or yellow
- Luster
- Dull to earthy
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Physical properties
Hardness: 1-3 on Mohs scale; Color: Reddish-brown, tan, or yellow; Luster: Dull to earthy; Crystal structure: Amorphous or microcrystalline; Cleavage: None; Pisolitic/Oolitic texture (pea-sized round inclusions).
Formation & geological history
Formed by the intense chemical weathering of rocks in tropical or subtropical climates with high rainfall, where silica is leached out and aluminum oxides are concentrated. Most deposits are of Cenozoic age.
Uses & applications
Primary ore of aluminum; used in the production of alumina (aluminum oxide) for industry, abrasives, refractories, and chemical processes.
Geological facts
Bauxite is named after the village of Les Baux in southern France, where it was first identified in 1821. It is not technically a single mineral but an aluminum-rich sedimentary rock also known as a 'laterite'.
Field identification & locations
Identify by its distinctive 'pea-like' or round pisolitic texture and earthy appearance. Found commonly in Guinea, Australia, Brazil, and Jamaica. Collectors look for pieces with well-defined, contrasting pisolites.
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