sedimentary
Bauxite (Laterite Clay)
Bauxite (mixture of Hydrous Aluminum Oxides: Gibbsite Al(OH)3, Boehmite and Diaspore AlO(OH))
Hardness: 1-3 on Mohs scale; Color: Reddish-brown, white, tan, and yellow; Luster: Dull/earthy; Crystal Structure: Amorphous/microcrystalline; Specific Gravity: 2.0-2.5.
- Hardness
- 1-3 on Mohs scale
- Color
- Reddish-brown, white, tan, and yellow
- Luster
- Dull/earthy
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Physical properties
Hardness: 1-3 on Mohs scale; Color: Reddish-brown, white, tan, and yellow; Luster: Dull/earthy; Crystal Structure: Amorphous/microcrystalline; Specific Gravity: 2.0-2.5.
Formation & geological history
Formed by 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 secondary aluminum and iron oxides. Most deposits are from the Cenozoic era.
Uses & applications
Primary source of aluminum metal; used in abrasives, refractories, chemicals (aluminum sulfate), and as a hydraulic fracturing proppant.
Geological facts
Bauxite is not a single mineral but a rock consisting of various aluminum hydroxides. It was first discovered in 1821 by Pierre Berthier near the village of Les Baux in France, which gives the rock its name.
Field identification & locations
Identify by its earthy appearance, pisolitic (pea-sized) structures often visible in specimens, and its soft, clay-like feel when scratched. Commonly found in Australia, Guinea, Brazil, and Jamaica. Collectors look for high iron content (darker red) or rare crystal inclusions.
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