Staurolite
Fe2+2Al9Si4O23(OH)IMA symbol: Stgrandfathered
Staurolite is a silicate mineral with the formula Fe2+2Al9Si4O23(OH), crystallizing in the monoclinic system. It has a Mohs hardness of 7-7.5, typically black, brown, red or yellow in color, with a resinous or vitreous luster, a specific gravity of 3.65-3.75. Its streak is gray or red; cleavage is distinct.
Photos
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Crystallography
| Crystal system | monoclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | C c m m |
| Cell (Å, °) | a = 7.886, b = 16.659, c = 5.671; α = 90, β = 90, γ = 90 |
| Cell volume | 745.016 ų, Z = 4 |
| Axial ratios | 0.4734:1:0.3404calculated from COD 9002795 |
| Source structure | COD 9002795 (American Mineralogist, 2002) — 1 of 66 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 8.329 | 1.398 | 7.128 | 1.984 | 2.699 | 3.017 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 71.8 | 68.7 | 41.7 | 37.7 | 37 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9002795; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 4.281 g/cm³calculated from COD 9002795 |
|---|---|
| Hardness (Mohs) | 7-7.5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.65-3.75 g/cm3single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Color | black, brown, red, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | gray, redsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | resinous, vitreousDana, System of Mineralogy, 6th ed. (1892) |
| Cleavage | distinctDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 9.AF.30Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.AF.30Wikidata (CC0) |