Chemical symbol Sb, Melting point 630C, Atomic number 51, Atomic mass 121.76 amu, Classification metalloid, crystal structure Rhombohedral. Colour, bluish. Name origin from the Greek words 'anti' (opposed) and 'monos' (solitude). Obtained from stibnite, valentinite. An element often found as a component in lead-based alloys or other white metal alloys. See 'Pewter'.