Mineral Information and Data:

Braunite
Mn2+Mn3+6O8SiO4 [CNMNC approved formula]

Named to honor Kammerrath [Advisor of the Chambers] Braun of Gotha, Germany.

IMA status : Valid species (Pre-IMA 1828) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
07.05.01.03  
  (07) Multiple Oxides
  (07.05) where A B X2
  (07.05.01) Humite group (Tetragonal: I41/acd) containing Si
  
Nickel-Strunz
(10th edition) :
09.AG.05
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AG) Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
  
Crystal system: Tetragonal System
Point group (H-M): 4/mmm (or 4/m 2/m 2/m) — ditetragonal-dipyramidal
Space group: I41/acd
Unit cell: a = 9.41(4) Å, c = 18.8(2) Å
Crystal Habit: As pyramidal crystals, to 5 cm, striated on {001} and {201} parallel on [010]; also dense granular, massive.
Twinning: On {112}
  
Color: Dark, brownish black to steel-gray; in polished section, greyish white with a brownish tinge.
Luster: Submetallic
Hardness (Mohs): 6 - 6.5
Measured Density: 4.72 - 4.83 g/cm3
Tenacity: Brittle
Streak: Brownish black to steel-gray
  
Polymorphism and Series: Forms a series with abswurmbachite.
Geologic Setting: Formed by metamorphism of manganese silicates and oxides; also a product of weathering.
Mineral Association: Pyrolusite, jacobsite, hausmannite, bixbyite, rhodonite, spessartine, hematite
  
Other Properties: Paramagnetic (weakly attracted to magnetic fields).

 

Braunite
Origin: Kacharwaki, Nagpu District, India
Sample size: 9.5 x 7 x 5 cm
Photo: Rob Lavinsky

 

Braunite
(zoom-in of above)

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