sedimentary
Bauxite
Bauxite (Mixture of Al(OH)3, AlO(OH), and Fe2O3)
Hardness: 1-3 Mohs; Color: reddish-brown, white, tan; Luster: earthy/dull; Structure: Pisolitic (pea-sized round grains) or massive; Specific Gravity: 2.0-2.5.
- Hardness
- 1-3 Mohs
- Color
- reddish-brown, white, tan
- Luster
- earthy/dull
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Physical properties
Hardness: 1-3 Mohs; Color: reddish-brown, white, tan; Luster: earthy/dull; Structure: Pisolitic (pea-sized round grains) or massive; Specific Gravity: 2.0-2.5.
Formation & geological history
Formed through the chemical weathering (laterization) of aluminum-rich rocks in tropical or subtropical climates. It is the primary ore for aluminum and often dates from the Mesozoic to Cenozoic eras.
Uses & applications
Primary source of aluminum; used in metallurgy, chemicals, abrasives, and refractory materials.
Geological facts
Bauxite is not a single mineral but a rock composed mainly of aluminum oxide minerals like gibbsite, boehmite, and diaspore. The red color is usually due to iron oxide impurities.
Field identification & locations
Identify by its distinctive 'pisolitic' circular grain pattern and earthy texture. It is lighter than it looks and lacks a crystalline sparkle. Commonly found in Guinea, Australia, Brazil, and Jamaica.
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