sedimentary
Bauxite
Alumina-rich rock (consisting of Gibbsite, Boehmite, and Diaspore)
Hardness: 1-3 Mohs, Color: Reddish-brown, pink, or gray, Luster: Dull/earthy, Crystal structure: Pisolitic (pea-like) or massive, Specific Gravity: 2.0-2.5
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Physical properties
Hardness: 1-3 Mohs, Color: Reddish-brown, pink, or gray, Luster: Dull/earthy, Crystal structure: Pisolitic (pea-like) or massive, Specific Gravity: 2.0-2.5
Formation & geological history
Formed as a residual soil in tropical or subtropical climates through the intense chemical weathering of rocks high in aluminum silicates. This process is known as lateritization.
Uses & applications
Primary ore for the production of aluminum. Also used in the manufacture of abrasives, refractories, chemicals, and aluminous cement.
Geological facts
Bauxite is not a single mineral but a mixture of hydrous aluminum oxides. It was first discovered in 1821 by Pierre Berthier near the village of Les Baux in southern France, which is where it gets its name.
Field identification & locations
Identify in the field by its distinct round, pea-shaped (pisolitic) structures and earthy smell when wet. Common in places like Australia, Guinea, and Brazil. Collectors should look for distinct nodules.
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