Jacobsite
Jacobsite is a manganese iron oxide mineral. It is in the spinel group and forms a solid solution series with magnetite. The chemical formula is MnFe2O4 or with oxidation states and substitutions:
2O4.
It occurs as a primary phase or as alteration of other manganese minerals during metamorphism of manganese deposits. Typical associated minerals include hausmannite, galaxite, braunite, pyrolusite, coronadite, hematite and magnetite. It is a ferrimagnetic substance, which is weakly attracted by a magnet.
It was first described in 1869 and named for the Jakobsberg Mine, Nordmark, Filipstad, Värmland, Sweden.
, Kalahari manganese fields, Northern Cape Province, South Africa. Size 3.8 x 3.5 x 3.2 cm
