Braunite

 Braunite is a silicate mineral containing both di- and tri-valent manganese with the chemical formula: Mn2+Mn3+6[O8|SiO4].[2] Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium.

Braunite
Braunit - San Marcel, Piemont.jpg
Braunite, from San Marcel, Piemonte , Italy
General
CategoryNesosilicates
Formula
(repeating unit)		Mn2+Mn3+6[O8|SiO4]
Strunz classification9.AG.05
Dana classification7.5.1.3
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupI41/acd
Identification
Colorbrownish black, steel-grey
Cleavage{112} perfect
Mohs scale hardness6-6+1⁄2
Lustersub-metallic
Streakblack
Diaphaneityopaque
Specific gravity4.72 - 4.83
References[1]

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.[2]

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.[3][4]

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License

Note

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License.