Tungsten features the lowest vapour pressure of all metals, very high moduli of compression and elasticity, very high thermal creep resistance, high thermal and electrical conductivity and, last but not least, a very high coefficient of electron emission. The latter can even be improved by alloying tungsten with certain metal oxides.
Most of these unusual properties are due to the half-filled 5d electron shell with a very high binding energy of the tungsten metal lattice. Based on these properties, tungsten, tungsten alloys and some tungsten compounds cannot be substituted in many important applications in different fields of modern technology.
Tungsten occurs in the natural state only in the form of chemical compounds with other elements. Although more than 20 tungsten bearing minerals are known, only two of them are important for industrial use, namely wolframite and scheelite.
Pure scheelite has blue-white fluorescence in ultraviolet light, a property which is utilised in prospecting.
Wolframite is a general term for iron and manganese tungstates where the iron/manganese ratio can vary. A mineral with more than 80% FeWO4 is called Ferberite and a mineral with more than 80% MnWO4 is called Hübnerite.