For lamp filaments. In 1779 Peter Woulfe examined the mineral now known as wolframite and concluded it must contain a new substance. Scheele and Berman suggested the possibility of obtaining a new metal by reducing this acid. Tungsten occurs in wolframite, scheelite, huebnertie, and ferberite. Important deposits of tungsten occur in California, Colorado, South Korea, Bolivia, Russia, and Portugal.
Natural tungsten contains five stable isotopes.
Twenty one other unstable isotopes are recognized. The metal is obtained commercially be recucing tungsten oxide with hydrogen or carbon. Very pure tungsten can be cut with a hacksaw, and can be forged, spun, drawn, and extruded. The impure metal is brittle and can be worked only with difficulty. Tungsten has the highest melting point of all metals, and at temperatures over 1650 o C has the highest tensile strength.