Wolframite, is a principal ore of tungsten. It is an iron and manganese tungstate mineral. It is monoclinic, with tabular crystals, has a hardness of 5 to 5.5 mhos, SG of 7.1 to 7.5, is dark grey, reddish brown, brownish black, or iron black in colour. Streak is dark red brown or black.
Wolframite is commonly found in granite and pegmatite dikes, and is often associated with cassiterite; it also occurs in sulfide veins and placer deposits. Because heat causes tungsten to expand at about the same rate as glass, the metal is widely used to make glass-to-metal seals. Tungsten or its alloys are used for filaments for electric lamps, electron and television tubes, electrical contact points for automobile distributors, heating elements for electrical furnaces, and space, missile, and high-temperature applications. Tungsten carbide is an important compound in the metal working, mining, and petroleum industries. Alloys such as high-speed steel, cristite, and stellite, used in high-speed tools, contain tungsten. Other important tungsten compounds are calcium and magnesium tungstate, which are used in fluorescent lighting, and tungsten disulphide, which is used as a high-temperature lubricant at temperatures up to 500 deg C. Tungsten compounds also find uses in the chemical, paint, and tanning industries.