Braunite
Mineral Mn7SiO12
About it
Black, submetallic manganese ore, massive or in sharp pyramids; the best crystals come from South Africa's Kalahari manganese field. Harder than other black manganese ores.
- Type
- Mineral
- Group
- Silicate (nesosilicate), braunite group
- Formula
- Mn7SiO12
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 4.72–4.83
- Streak
- brownish black to steel grey
- Lustre
- submetallic
- Crystal system
- Tetragonal
- Colours
- brownish black, steel grey
- Transparency
- opaque
- Cleavage and fracture
- perfect pyramidal; uneven fracture
- Magnetic
- Weakly
Typical values: real specimens vary. For more, see mindat.org.