Chemistry:Jacobsite

From HandWiki
Jacobsite
Jacobsite-cktsr-15a.jpg
General
CategoryOxide minerals
Spinel group
Spinel structural group
Formula
(repeating unit)
iron(II,III) manganese oxide, MnFe2O4
Strunz classification4.BB.05
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFd3m
Unit cella = 8.457 Å; Z = 8
Identification
ColorBlack to brownish black
Crystal habitDisseminated to massive, rarely as octahedral crystals
TwinningSpinel law, flattened on {111} or lamellar
Cleavage{111}, probably a parting
FractureConchoidal
Mohs scale hardness5.5 - 6.5
|re|er}}Metallic
Streakreddish black to brown
DiaphaneityOpaque
Specific gravity4.76
Optical propertiesIsotropic
Refractive index~�2.3
Other characteristicsweakly magnetic
References[1][2]

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: (Mn2+,Fe2+,Mg)(Fe3+,Mn3+)2O4.[1][3]

It occurs as a primary phase or as alteration of other manganese minerals during metamorphism of manganese deposits.[3] Typical associated minerals include hausmannite, galaxite, braunite, pyrolusite, coronadite, hematite and magnetite.[1] 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.[2]

Jacobsite, N'Chwaning Mines, Kuruman, Kalahari manganese fields, Northern Cape Province, South Africa. Size 3.8 x 3.5 x 3.2 cm

References