Wolframite

Wolframite is a tungstate of iron and manganese crystallising in the monoclinic system. Crystals are commonly tabular or prismatic. It is a heavy mineral with a specific gravity of 7 to 7.5 and hardness of 5 to 5.5. It is dark brown or black in colour. Its streak is black and its lustre is sub-metallic Wolframite is used as an ore of tungsten.