Hübnerite
Hübnerite or hubnerite is a mineral consisting of manganese tungstate (chemical formula: MnWO4). It is the manganese endmember of the manganese - iron wolframite solid solution series. It forms reddish brown to black monoclinic prismatic submetallic crystals. The crystals are typically flattened and occur with fine striations. It has a high specific gravity of 7.15 and a Mohs hardness of 4.5. It is transparent to translucent with perfect cleavage. Refractive index values are nα=2.170 - 2.200, nβ=2.220, and nγ=2.300 - 2.320.
Typical occurrence is in association with high-temperature hydrothermal vein deposits and altered granites with greisen, granite pegmatites and in alluvial deposits.
It was first described in 1865 and named after the German mineralologist, Adolf Huebner.
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