sedimentary
Bauxite
AlOx(OH)3-2x (mixture of Gibbsite, Boehmite, and Diaspore)
Hardness: 1-3 Mohs; Color: Brownish-red, pink, or gray; Luster: Dull to earthy; Crystal structure: Amorphous/massive; Cleavage: None; Specific gravity: 2.0-2.5
- Hardness
- 1-3 Mohs
- Color
- Brownish-red, pink, or gray
- Luster
- Dull to earthy
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Physical properties
Hardness: 1-3 Mohs; Color: Brownish-red, pink, or gray; Luster: Dull to earthy; Crystal structure: Amorphous/massive; Cleavage: None; Specific gravity: 2.0-2.5
Formation & geological history
Formed through the intense chemical weathering (laterization) of aluminum-rich rocks in tropical or subtropical climates with high rainfall. It is primarily found in Cenozoic deposits but can date back to the Mesozoic.
Uses & applications
Primary ore of aluminum worldwide. Used in the production of alumina (Bayer process), refractories, abrasives, chemicals, and portland cement.
Geological facts
Bauxite is not technically a mineral but a rock composed mainly of aluminum oxide minerals. It was named after the village Les Baux in southern France where it was first identified in 1821.
Field identification & locations
Identified in the field by its distinct 'pisolitic' (pea-like) circular structures, earthy smell when damp, and red-brown iron staining. Commonly found in surface deposits in Australia, Guinea, Brazil, and Jamaica.
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