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Bauxite, important ore of aluminum, consisting of aluminum oxide of various degrees of hydration, usually mixed with impurities, particularly iron oxides and hydroxides. Among the specific aluminum-bearing minerals in bauxite are gibbsite, Al(OH)3, and diaspore, HAlO2. Bauxite is a soft mineral with hardness varying from 1 to 3 and specific gravity from 2 to 2.55. In color it may vary from white to brown, and it is dull in appearance. Bauxite usually occurs in aggregates in lumps about the size of a pea. Although aluminum is the commonest of all metals on the surface of the earth, it most frequently occurs strongly bound in silicate minerals, which cannot be used commercially as ores because of the difficulty of extracting the aluminum. Bauxite, on the other hand, forms by the rapid weathering of granitic rocks in warm, humid climates and can be easily purified and converted directly into either alum or metallic aluminum. Bauxite is mined in large quantities in Australia, Guinea, and Jamaica. Annual world production in 1993 was about 101 million metric tons.
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