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Formula: Mg2Mn3+O2(BO3)
Anhydrous monoborate,
ludwigite group
Crystal System: Orthorhombic
Specific gravity: 3.84 measured, 3.80 calculated
Hardness: 6
Streak: Yellowish brown
Colour: Reddish brown
Environments
Localities
At the type locality, Långban, Filipstad, Värmland County, Sweden, fredrikssonite occurs in
dolomite in a metamorphosed iron-manganese orebody. It has
been found here in
two assemblages. In one sample it was associated with calcite,
adelite, brucite and
hausmannite; in another sample it was found with
clinohumite, calcite and
jacobsite
(AM 71.227).
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