The average cost of antimony ore per ton is $5.50. It is a chemical element, represented by the symbol Sb. It has an atomic number of 51. It is silvery grey and lustrous in appearance. It is found mainly as the sulfide mineral stibnite. Its components are important fire retardants, found in many domestic and commercial products. It is used in the making of flame-proofing compounds in the form of antimony trioxide. It forms a useful alloy with lead, increasing its hardness and strength.