sedimentary
Bauxite
Bauxite (mixture of Gibbiste Al(OH)3, Boehmite ̳-AlO(OH), and Diaspore ́-AlO(OH))
Hardness: 1-3 (Mohs scale), Color: White, gray, yellow, or earthy red/brown, Luster: Dull to earthy, Crystal Structure: Amorphous/microcrystalline mixture, Cleavage: None/Pisolithic texture, Specific Gravity: 2.0-2.5
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Physical properties
Hardness: 1-3 (Mohs scale), Color: White, gray, yellow, or earthy red/brown, Luster: Dull to earthy, Crystal Structure: Amorphous/microcrystalline mixture, Cleavage: None/Pisolithic texture, Specific Gravity: 2.0-2.5
Formation & geological history
Formed through the intense chemical weathering of rocks in hot, humid, tropical or subtropical climates. It is a residual soil (laterite) from which silica and other soluble materials have been leached, leaving behind concentrated aluminum oxides.
Uses & applications
The primary ore of aluminum. Used to produce alumina (aluminum oxide) via the Bayer process, which is then used to create aluminum metal, abrasives, refractories, and chemicals.
Geological facts
Named after the village Les Baux in southern France where it was first identified in 1821. It is not actually a single mineral but a mixture of hydrous aluminum oxides and various impurities like iron oxides and clay.
Field identification & locations
Identified in the field by its unique 'pisolithic' or pea-like structure which looks like small rounded stones cemented together. It is commonly found in topsoil layers across Australia, Guinea, Brazil, and Jamaica.
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