Aluminium is one of the most common elements on earth, second only to oxygen and silicon. In nature, it is always found combined with other elements; it is present in many minerals. From an industrial point of view, this light metal (its density is 2.71 g/cm³) is extracted from bauxite, a reddish brown or yellow rock, found mainly in the US, Russia, Guyana, Hungary, the territories of former Yugoslavia.