Aluminum


Most of the aluminum produced today is made from bauxite. The only other ore serving as a raw material for aluminum is nepheline, a sodium potassium aluminum silicate.

Bauxite derives its name from the village of Les Bauxs in Southern France where it was discovered in 1821. The term is generic. It refers to an ore or to a mixture of minerals rich in hydrated oxides, formed of aluminous rocks such as nepheline, feldspars, serpentine, clays, etc. During weathering the silicates are decomposed and the decomposition products (silica, lime, soda, potash, etc.) are leached out, leaving behind a residue enriched in alumina, iron oxide, and titanium oxide but still containing some silica. In tropical and subtropical regions the weathering process is more intense, and this is where most of the large bauxite deposits are found, at or near the surface.

Most bauxite contains 40-60% alumina, either as the trihydrate gibbsite or as the monohydrates boehmite and diaspore. Boehmite prevails in bauxite found in a broad belt along the Northern Mediterranean. These deposits, extending from Spain through Southern France, Italy, ex-Yugoslavia, Austria, and Hungary to Greece, provide the base for the European aluminum industry. The biggest gibbsite deposits are found in tropical regions.