Hübnerite
| Hubnerite | |
|---|---|
Hubnerite from Silverton District, San Juan County, Colorado (Size: 8.5 x 6.6 x 4.3 cm)
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| General | |
| Category | Oxide minerals |
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Formula (repeating unit) |
MnWO4 |
| Strunz classification | 4.DB.30 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/c |
| Unit cell | a = 4.86, b = 5.78 c = 5.02 [Å]; β = 90.816°, Z = 4 |
| Identification | |
| Color | Yellowish brown to reddish brown, blackish brown, black; Deep red internal reflections in reflected light |
| Crystal habit | Prismatic striated crystals, tabular to flattened, in radiating groups |
| Twinning | Contact twins |
| Cleavage | Perfect on {010} |
| Fracture | Irregular/uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 4-4½ |
| Luster | Metallic to adamantine towards resinous. |
| Streak | Yellow to reddish brown, greenish gray |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 7.12 - 7.18 |
| Optical properties | Biaxial (+) |
| Refractive index | 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 angle | 73° measured |
| References | |
Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula: MnWO4, it isn't a tungstate). 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 occurs associated with cassiterite, arsenopyrite, molybdenite, tourmaline, topaz, rhodochrosite and fluorite.
It was first described in 1865 for an occurrence in the Erie and Enterprise veins, Mammoth district, Nye County, Nevada, and named after the German mining engineer and metallurgist, Adolf Hübner from Freiberg, Saxony.
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