Antimony

Refined antimony is a brittle, silvery-white metalloid used primarily as a hardening agent in lead alloys. The addition of 3–12% antimony to lead significantly increases its hardness and tensile strength, making antimonial lead the standard material for lead-acid battery plates and most modern ammunition. Antimony is also used as a flame retardant compound, in certain semiconductors, and as a constituent of type metal for printing. Stibnite, its principal ore, is straightforward to smelt but antimony's toxicity demands careful handling throughout the process.