sedimentary
Bauxite
Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))
Hardness: 1-3 (Mohs scale); Color: Dull reddish-brown, tan, or white with mottled patterns; Luster: Earthy, dull; Structure: Pisolitic (pea-sized round grains) or massive; Cleage: None; Specific Gravity: 2.0-2.5
- Hardness
- 1-3 (Mohs scale)
- Color
- Dull reddish-brown, tan, or white with mottled patterns
- Luster
- Earthy, dull
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Physical properties
Hardness: 1-3 (Mohs scale); Color: Dull reddish-brown, tan, or white with mottled patterns; Luster: Earthy, dull; Structure: Pisolitic (pea-sized round grains) or massive; Cleage: None; Specific Gravity: 2.0-2.5
Formation & geological history
Formed through the intense chemical weathering of rocks (like granite or basalt) in tropical or subtropical climates with high rainfall, which leaches away silica and leaves behind aluminum oxides. Age varies from Paleozoic to Cenozoic.
Uses & applications
Primary ore of aluminum used in construction, transportation (aerospace/automotive), and packaging. Also used in refractories, abrasives, and chemical production.
Geological facts
Bauxite is not a mineral but a rock composed mainly of aluminum-rich minerals like gibbsite, boehmite, and diaspore. The red color is typically due to iron oxide (hematite or goethite) impurities.
Field identification & locations
Identify by its 'pisolitic' texture (looking like it is made of small stuck-together pebbles) and earthy, clay-like appearance. Commonly found in Australia, Guinea, Brazil, and Jamaica. Collectors look for high-iron 'red' specimens or those with distinct large pisolites.
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