sedimentary
Bauxite
Bauxite (mixture including Gibbsite Al(OH)3, Boehmite γ-AlO(OH), and Diaspore α-AlO(OH))
Hardness: 1–3 Mohs; Color: Brown, reddish-brown, grayish; Lustre: Dull, earthy; Structure: Pisolitic (pea-like) or massive; Cleavage: None; Specific Gravity: 2.0–2.5
- Hardness
- 1–3 Mohs
- Color
- Brown, reddish-brown, grayish
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Physical properties
Hardness: 1–3 Mohs; Color: Brown, reddish-brown, grayish; Lustre: Dull, earthy; Structure: Pisolitic (pea-like) or massive; Cleavage: None; Specific Gravity: 2.0–2.5
Formation & geological history
Formed through the intense chemical weathering of rocks (commonly aluminum-rich basalt or limestone) in hot, humid tropical or subtropical climates, mostly during the Cenozoic era. The location near Visakhapatnam, India, is famous for East Coast Bauxite deposits formed from Khondalite and Charnockite rocks.
Uses & applications
Primary ore of aluminum world-wide; used in the manufacturing of aluminum metal, abrasives, refractories, and chemicals.
Geological facts
Bauxite is not a single mineral but a sedimentary rock composed mainly of aluminum hydroxides. Australia, Guinea, and India are among the top global producers. The Eastern Ghats of India are globally significant for their high-grade bauxite reserves.
Field identification & locations
Identify by its earthy, clay-like appearance, red-brown color from iron impurities, and sometimes pea-sized round structures (pisolites). In the field, it is often found as a cap rock (laterite) on plateaus in tropical regions.
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