A light white metal, ductile and malleable, and a good conductor of electricity. It occurs widely in nature in clays and is the third most abundant element in the Earth's crust. It is extracted mainly from bauxite by electrolysis of a molten mixture of purified bauxite and cryolite. The metal and its alloys are used for aircraft, cooking utensils, electrical apparatus, and for many other purposes where its light weight is an advantage. Aluminium became implicated as an environmental health hazard in the 1980s on two counts. Biomedical scientists looking for possible causes of Alzheimer's disease, the premature senility indicated by loss of memory and confusion, found a circumstantial link with aluminium. The theory is a controversial one.