Chemical symbol Al. Atomic weight 26.98, atomic number 13, mp 660, 37 C, specific gravity 2.69. It is the most abundant of the metallic elements but it is very difficult to extract and was not properly known until 1825. It is predominantly extracted from bauxite. Aluminium alloys are widely used today. They are light with good corrosion resistance and have excellent casting, hot and cold working, and welding properties.