Pyrolusite
Mineral MnO2
Also called Polianite
About it
Sooty black masses that blacken the fingers, and radiating needles, with a black streak. A common manganese ore; many black 'dendrites' on rock faces are mixed manganese oxides rather than pure pyrolusite.
- Type
- Mineral
- Group
- Oxide, rutile group
- Formula
- MnO2
- Hardness (Mohs)
- 2–6.5
- Specific gravity
- 4.4–5.1
- Streak
- black to bluish black
- Lustre
- metallic, dull, earthy
- Crystal system
- Tetragonal
- Colours
- black, steel grey
- Transparency
- opaque
- Cleavage and fracture
- perfect prismatic; uneven fracture, soft masses soil the fingers
Typical values: real specimens vary. For more, see mindat.org.