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 na=2.170 - 2.200, nß=2.220, and n?=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 mineralogist, Adolf Huebner.