hübnerite

{{Infobox mineral | name = Hubnerite | image = Hübnerite - Pasto Bueno, Ancash, Peru.jpg | imagesize = 270px | alt = | caption = | category = Oxide minerals | formula = | IMAsymbol = Hbr | molweight = | strunz = 4.DB.30 | dana = | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P21/c | unit cell = a = 4.86, b = 5.78 c = 5.02 [Å]; β = 90.816°, Z = 4 | color = Yellowish brown to reddish brown, blackish brown, black; Deep red internal reflections in reflected light | colour = | habit = Prismatic striated crystals, tabular to flattened, in radiating groups | twinning = Contact twins | cleavage = Perfect on {010} | fracture = Irregular/uneven | tenacity = Brittle | mohs = 4– | luster = Metallic to adamantine towards resinous. | streak = Yellow to reddish brown, greenish gray | diaphaneity = Transparent to translucent | gravity = 7.12–7.18 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα=2.17–2.2, nβ=2.22, nγ=2.3–2.32 | birefringence = 0.1200–0.1300 | pleochroism = Perceptible; X = yellow to green, red-orange; Y = yellowish brown to greenish yellow, red-orange to red; Z = green; brick-red to red | 2V = 73° measured | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }}

Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (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.