a hard malleable ductile greyish-white element. It occurs principally in wolframite and scheelite and is used in lamp filaments, electrical contact points, X-ray targets, and, alloyed with steel, in high-speed cutting tools. Symbol: W; atomic no: 74; atomic wt: 183.85; valency: 2–6; relative density: 19.3; melting pt: 3422±20°C; boiling pt: 5555°C