Arfvedsonite
NaNa2(Fe2+4Fe3+)Si8O22(OH)2IMA symbol: Arfredefined
Arfvedsonite is a silicate mineral with the formula NaNa2(Fe2+4Fe3+)Si8O22(OH)2, crystallizing in the monoclinic system. It has a Mohs hardness of 6, typically black or green in color, with a vitreous luster, a specific gravity of 3.44-3.45. Its streak is gray.
Photos
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Crystallography
| Crystal system | monoclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | C 1 2/m 1 |
| Cell (Å, °) | a = 9.84, b = 18.036, c = 5.365; α = 90, β = 104.05, γ = 90 |
| Cell volume | 923.665 ų, Z = 2 |
| Axial ratios | 0.5456:1:0.2975calculated from COD 9010042 |
| Source structure | COD 9010042 (American Mineralogist, 1993) — 1 of 3 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 8.437 | 2.727 | 3.133 | 2.561 | 3.423 | 2.603 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 64.3 | 42.6 | 38.5 | 27.4 | 25.4 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9010042; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.389 g/cm³calculated from COD 9010042 |
|---|---|
| Hardness (Mohs) | 6single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.44-3.45 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | black, greensingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | graysingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Luster | vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Classification
| Nickel-Strunz (10th) | 9.DE.25Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 9.DE.25Wikidata (CC0) |