sedimentary
Bauxite
Bauxite (Al2O3·nH2O)
Hardness: 1-3 Mohs, Color: Reddish-brown to tan, Luster: Dull/Earthy, Crystal Structure: Amorphous/Pisolitic, Cleavage: None, Specific Gravity: 2.0-2.5
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Physical properties
Hardness: 1-3 Mohs, Color: Reddish-brown to tan, Luster: Dull/Earthy, Crystal Structure: Amorphous/Pisolitic, Cleavage: None, Specific Gravity: 2.0-2.5
Formation & geological history
Formed by the intense chemical weathering of rocks in tropical or subtropical climates, resulting in the leaching of silica and the concentration of aluminum oxides and hydroxides. Most deposits are Cenozoic in age.
Uses & applications
Primary ore for aluminum production. Also used in abrasives, refractories, and chemical industries. Low-grade specimens have little decorative use.
Geological facts
Bauxite is not a mineral itself but a mixture of aluminum hydroxide minerals like gibbsite, boehmite, and diaspore. The term was coined in 1821 after the village of Les Baux in France.
Field identification & locations
Identified by its distinctive pea-sized round structures called pisolites and its earthy, clay-like appearance. Commonly found in Australia, Guinea, Brazil, and Jamaica.
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