Hübnerite

hubnerite

molybdenite

ferberite

rhodochrosite

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Formula: Mn2+(WO4)
Anhydrous tungstate, as given by Dana, but according to Mindat this is a misclassification; there are no WO4 tetrahedra in it, so it should be classified as an oxide. Wolframite Group, columbite supergroup, Manganese-bearing mineral.
Hübnerite forms a complete solid solution series with ferberite.
Crystal System: Monoclinic
Specific gravity: 7.12 to 7.18 measured, 7.234 calculated
Hardness: 4 to 4½
Streak: Greenish-grey, yellow to reddish-brown
Colour: Yellow-brown, reddish-brown, blackish brown, black, red (rare)
Environments:

Pegmatites
Sedimentary environments
Metamorphic environments
Hydrothermal environments

Hübnerite occurs in high-temperature (hypothermal) hydrothermal veins and medium temperature metamorphic rocks. It also occurs in granite pegmatites and in alluvial and residual deposits.
Associated minerals include cassiterite, arsenopyrite, molybdenite, tourmaline, topaz, rhodochrosite and fluorite.

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