Braunite
Mn2+Mn3+6O8(SiO4)IMA symbol: Bntgrandfathered
Braunite is a silicate mineral with the formula Mn2+Mn3+6O8(SiO4), crystallizing in the tetragonal system. It has a Mohs hardness of 6-6.5, typically black, brown or gray in color, with a metallic or submetallic luster, a specific gravity of 4.75-4.82. Its streak is black.
Photos
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Crystallography
| Crystal system | tetragonal crystal systemWikidata (CC0) |
|---|---|
| Space group | I 41/a c d :2 |
| Cell (Å, °) | a = 9.408, b = 9.408, c = 18.668; α = 90, β = 90, γ = 90 |
| Cell volume | 1652.31 ų, Z = 8 |
| Axial ratios | 1.0000:1:1.9843calculated from COD 9000532 |
| Source structure | COD 9000532 (American Mineralogist, 1976) — 1 of 11 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 2.709 | 1.657 | 1.417 | 2.352 | 1.663 | 1.409 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 30.7 | 16.7 | 12.7 | 12 | 11.1 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9000532; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 4.861 g/cm³calculated from COD 9000532 |
|---|---|
| Hardness (Mohs) | 6-6.5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 4.75-4.82 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | black, brown, graysingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | blacksingle sourceWikidata (CC0) |
| Luster | metallic, submetallicsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 9.AG.05Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.AG.05Wikidata (CC0) |