A silvery-white, ductile metallic element, the most abundant in the earth's crust but found only in combination, chiefly in bauxite. Having good conductive and thermal properties, it is used to form many hard, light, corrosion-resistant alloys. Atomic number 13; atomic weight 26.9815; melting point 660.32°C; boiling point 2,519°C; specific gravity 2.70; valence 3. See Periodic Table.