Hercynite
Fe2+Al2O4IMA symbol: Hcgrandfathered
Hercynite is an oxide or hydroxide mineral with the formula Fe2+Al2O4, crystallizing in the cubic system. It has a Mohs hardness of 7.5-8, typically black in color, with a dull or vitreous luster, a specific gravity of 3.91-3.95. Its streak is gray or green.
Photos
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Crystallography
| Crystal system | cubic crystal systemWikidata (CC0) |
|---|---|
| Space group | F d -3 m :2 |
| Cell (Å, °) | a = 8.1584, b = 8.1584, c = 8.1584; α = 90, β = 90, γ = 90 |
| Cell volume | 543.019 ų, Z = 8 |
| Axial ratios | 1.0000:1:1.0000calculated from COD 9013620 |
| Source structure | COD 9013620 (American Mineralogist, 2009) — 1 of 75 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 2.46 | 2.884 | 1.442 | 1.57 | 1.665 | 2.04 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 57.9 | 54.7 | 43.5 | 17.7 | 15.9 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9013620; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 4.144 g/cm³calculated from COD 9013620 |
|---|---|
| Hardness (Mohs) | 7.5-8single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.91-3.95 g/cm3single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Color | blacksingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | gray, greensingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | dull, vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 4.BB.05Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 4.BB.05Wikidata (CC0) |
| Dana (8th) | 7.2.1.3Wikidata (CC0) |