Category Nesosilicates Strunz classification 9.AG.05 Crystal system Tetragonal | Formula(repeating unit) MnMn6[O8|SiO4] Dana classification 7.5.1.3 | |
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Crystal class Ditetragonal dipyramidal (4/mmm)H-M symbol: (4/m 2/m 2/m) | ||
Braunite is a silicate mineral containing both di- and tri-valent manganese with the chemical formula: Mn2+Mn3+6[O8|SiO4]. Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium.
Braunite forms grey/black tetragonal crystals and has a Mohs hardness of 6 - 6.5.
It was named after the Wilhelm von Braun (1790–1872) of Gotha, Thuringia, Germany.
A calcium iron bearing variant, named braunite II (formula: Ca(Mn3+,Fe3+)14SiO24), was discovered and described in 1967 from Kalahari, Cape Province, South Africa.
References
Braunite Wikipedia(Text) CC BY-SA