sedimentary
Bauxite
Bauxite (Al(OH)3, AlO(OH))
Hardness: 1-3 Mohs; Color: Reddish-brown, pink, yellow, or grey; Luster: Dull/earthy; Structure: Pisolitic (pea-sized round grains) or massive; Specific Gravity: 2.0-2.5
- Hardness
- 1-3 Mohs
- Color
- Reddish-brown, pink, yellow, or grey
- Luster
- Dull/earthy
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Physical properties
Hardness: 1-3 Mohs; Color: Reddish-brown, pink, yellow, or grey; Luster: Dull/earthy; Structure: Pisolitic (pea-sized round grains) or massive; Specific Gravity: 2.0-2.5
Formation & geological history
Formed by the intense chemical weathering of rocks in hot, humid tropical or subtropical climates. It is the result of the leaching of silica and other soluble materials, leaving behind aluminum oxides. Most deposits are from the Mesozoic or Cenozoic eras.
Uses & applications
Primary ore of aluminum. Used in the production of aluminum metal, refractory materials, chemicals, and abrasives.
Geological facts
Bauxite is not a single mineral but a mixture of hydrous aluminum oxides like gibbsite, boehmite, and diaspore. The red color is typically due to the presence of hematite (iron oxide).
Field identification & locations
Identify by its distinctive 'pisolitic' texture (looking like it is made of small stuck-together pebbles) and its earthy smell when damp. Found globally in belts like Jamaica, Australia, Guinea, and Brazil.
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