Bauxite, alumina and aluminium

The term bauxite is applied to certain consolidated or semi-consolidated rocks in which hydrated oxides of aluminium are the most important constituents in an aggregate which also contains a variety of impurities. Although bauxite has a number of industrial uses, the development of a large mining industry and extensive world trade in the commodity reflects the fact that it has proved to be the raw material from which it is possible to produce alumina at lowest cost. Alumina is the name commonly applied to the pure anhydrous oxide of aluminium. The conversion of bauxite to alumina on an industrial scale involves solution, recrystallisation and calcination. In turn, althougH alumina also has a number of uses in its own right, its main industrial importance is as the raw material from which aluminium metal is produced in electrolytic smelters. Bauxite was formerly mined in Northern Ireland but the production of aluminium in the United Kingdom is now entirely based on imported alumina. In 1976 total United Kingdom production of aluminium metal exceeded 0.5M tonnes.