Braunite-II Mineral Data

General Braunite-II Information

Chemical Formula:

Mn++Mn+++6SiO12

Composition:

Molecular Weight = 604.64 gm

Manganese 63.60 % Mn 11.73 % MnO / 78.33 % Mn₂O₃

Silicon 4.64 % Si 9.94 % SiO₂

Oxygen 31.75 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺Mn³⁺₆SiO₁₂

Environment:

Manganese oxide mineral deposits. Metamorphic and secondary weathering environments

IMA Status:

Not Approved IMA 1967

Locality:

Metamorphic, hydrothermal, and sedimentary rocks. Link to MinDat.org Location Data.

Name Origin:

Named after K. Braun (1790-1872) from Gotha, Germany.

Name Pronunciation:

Braunite-II

Braunite-II Image

Images:

Braunite-II Braunite-I

Comments: Crystals of braunite.
Location: Black Rock Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Scale: Crystal size 1.3 cm.
© John Veevaert

Braunite-II Crystallography

Axial Ratios:

a:c = 1:1.9904

Cell Dimensions:

a = 9.38, c = 18.67, Z = 8; V = 1,642.67 Den(Calc)= 4.89

Crystal System:

Tetragonal - Ditetragonal DipyramidalH-M Symbol (4/m 2/m 2/m) Space Group: I 4₁/acd

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.72(1), 1.656(0.7), 2.14(0.5),

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Forms: ( 1 3 1) ( 1 3 3) ( 0 1 1) ( 1 1 0) ( 0 0 1)

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Physical Properties of Braunite-II

Cleavage:

{111} Perfect

Color:

Grayish black, Brownish gray, Dark brownish black.

Density:

4.72 - 4.82, Average = 4.76

Diaphaneity:

Opaque

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Hardness:

6-6.5 - Orthoclase-Pyrite

Luster:

Sub Metallic

Magnetism:

Nonmagnetic

Streak:

brownish gray black

Optical Properties of Braunite-II

Optical Data:

NCalc= 2.37 - from Gladstone-Dale relationship (KC = 0.2796) where Ncalc=Dcalc*KC+1
NCalc= 2.33 - from Gladstone-Dale relationship (KC = 0.2796) where Ncalc=Dmeas*KC+1

Calculated Properties of Braunite-II

Electron Density:

Bulk Density (Electron Density)=4.61 gm/cc
note: Specific Gravity of Braunite-II =4.89 gm/cc.

Fermion Index:

Fermion Index = 0.0023216105
Boson Index = 0.9976783895

Photoelectric:

PE_Braunite-II= 16.86 barns/electron
U=PE_Braunite-II x rElectron Density= 77.73 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Braunite-II is Not Radioactive

Braunite-II Classification

Dana Class:

07.05.01.03 (07)Multiple Oxides

(07.05)where A B X2

(07.05.01)Humite group (Tetragonal: I41/acd) containing Si

07.05.01.01 Braunite-I MnMn6SiO12 I 4₁/acd 4/m 2/m 2/m

07.05.01.02 Neltnerite CaMn6SiO12 I 4₁/acd 4/m 2/m 2/m

07.05.01.03 Braunite-II* MnMn6SiO12 I 4₁/acd 4/m 2/m 2/m

07.05.01.04 Abswurmbachite CuMn6SiO12 I 4₁/acd 4/m 2/m 2/m

Strunz Class:

09.AG.05 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AG -Nesosilicates with additional anions; cations in > [6] ± [6] coordination

09.AG.05 Abswurmbachite CuMn6SiO12 I 4₁/acd 4/m 2/m 2/m

09.AG.05 Braunite-I MnMn6SiO12 I 4₁/acd 4/m 2/m 2/m

09.AG.05 Braunite-II* MnMn6SiO12 I 4₁/acd 4/m 2/m 2/m

09.AG.05 Neltnerite CaMn6SiO12 I 4₁/acd 4/m 2/m 2/m

Other Braunite-II Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Bull.Miner.,Vol.107-111,1984-1988)

See Also:

Links to other databases for Braunite-II :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Print or Cut-and-Paste your Braunite-II Specimen Label here :

Braunite-II

Mn++Mn+++6SiO12
Dana No: 07.05.01.03 Strunz No: 09.AG.05
Locality:

Notes: