Pyrolusite
Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese. It is a black, amorphous appearing mineral, often with a granular, fibrous, or columnar structure, sometimes forming reniform crusts. It has a metallic luster, a black or bluish-black streak, and readily soils the fingers. The specific gravity is about 4.8. Its name is from the Greek for fire and to wash, in reference to its use as a way to remove tints from glass.
| Pyrolusite | |
|---|---|
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | MnO2 |
| IMA symbol | Pyl |
| Strunz classification | 4.DB.05 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | P42/mnm |
| Identification | |
| Color | Darkish, black to lighter grey, sometimes bluish |
| Crystal habit | Granular to massive: botryoidal. Crystals rare |
| Twinning | {031}, {032} may be polysynthetic |
| Cleavage | Perfect on 110 |
| Fracture | Irregular/Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 6–6.5, 2 when massive |
| Luster | Metallic, dull to earthy |
| Streak | Black to bluish-black |
| Specific gravity | 4.4–5.06 |
| Refractive index | Opaque |
| References | |
| Major varieties | |
| Polianite | pseudomorphic after manganite |
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