Bauxite: the principal ore of aluminium

Composition and appearance

Typical bauxite contains a combination of aluminium hydroxides such as gibbsite, boehmite and diaspore, together with iron oxides like goethite and hematite. Common gangue minerals include kaolinite and traces of titanium dioxide such as anatase. Grain size, colour and hardness vary with genesis and impurity content; colours range from white and tan to reddish brown.

Formation and major deposits

Bauxite forms primarily by intense chemical weathering of alumina-rich rocks in tropical and subtropical climates. Two main deposit types are lateritic (from prolonged weathering of silicate rocks) and karstic (formed in carbonate terrains). Major producing countries include Australia, Brazil, China and India, and historically significant deposits were first described near Les Baux-de-Provence, where Pierre Berthier identified the rock in 1821. Large open-pit operations are typical where ore bodies are shallow.

Processing and uses

Industrial processing separates alumina from impurities, most commonly by caustic leaching (the Bayer process) which dissolves aluminium compounds and leaves a solid residue known as red mud. The recovered alumina is then converted to metal by electrolysis in the Hall–Héroult process. The vast majority of bauxite is consumed for aluminium production; smaller amounts are used in abrasives, refractory materials and as raw material in certain chemicals and cement additives.

Environmental and economic aspects

Bauxite mining and refining have environmental footprints: land clearing for pits, handling and disposal of red mud, and energy-intensive smelting that produces greenhouse gases. Responsible practices include progressive rehabilitation of mined land, red mud treatment or reuse, and energy efficiency in refining and smelting. Bauxite remains economically important because aluminium is lightweight, recyclable and central to transportation, packaging and construction.

Notable facts

• Bauxite is mined by surface methods in most deposits and then upgraded for alumina extraction.
• Its name reflects its place of discovery at Les Baux-de-Provence and early 19th-century study by Berthier.
• Large, modern producers include Australia, Brazil, China and India; reserves and trade patterns affect aluminium prices globally.