Jacobsite
Mineral MnFe2O4
About it
Black octahedral grains of manganese iron spinel, weakly magnetic, in manganese ore bodies. Named for Jakobsberg, Sweden; also found at Långban and in the Kalahari manganese field of South Africa.
- Type
- Mineral
- Group
- Oxide, spinel group
- Formula
- MnFe2O4
- Hardness (Mohs)
- 5.5–6.5
- Specific gravity
- 4.7–5.1
- Streak
- reddish black
- Lustre
- metallic, submetallic
- Crystal system
- Isometric (cubic)
- Colours
- black, brownish black
- Transparency
- opaque
- Cleavage and fracture
- none; uneven to conchoidal fracture
- Magnetic
- Weakly
Typical values: real specimens vary. For more, see mindat.org.