The solid matter of the earth’s crust is made up of nearly a hundred elements, the most abundant of which are oxygen, silicon, and then aluminium. So aluminium is the third most common element and in the form of various compounds the metal is very widely distributed. Minute traces of aluminium salts are found in many foods for example, and the element is one of those around which evolution on this planet has developed. Aluminium, unlike some other metals, does not occur naturally in its pure metallic form. Only certain of the multitude of aluminium-bearing minerals may be regarded as ores, since extraction from many of them is currently too uneconomical. Commercial ores are grouped under the generic term ‘bauxite’, derived from the medieval village of Les Baux in Southern France, where high concentrations of hydrated aluminium oxide are found, and where early mining of the ore took place.