Orpiment
As2S3IMA symbol: Orpgrandfathered
Orpiment is a sulfide or sulfosalt mineral with the formula As2S3, crystallizing in the monoclinic system. It has a Mohs hardness of 1.5-2, typically yellow in color, with a pearly or resinous luster, a specific gravity of 3.4-3.5. Its streak is yellow; cleavage is perfect.
Photos
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Crystallography
| Crystal system | monoclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | P 1 21/n 1 |
| Cell (Å, °) | a = 11.475, b = 9.577, c = 4.256; α = 90, β = 90.68, γ = 90 |
| Cell volume | 467.685 ų, Z = 4 |
| Axial ratios | 1.1982:1:0.4444calculated from COD 9008211 |
| Source structure | COD 9008211 (Zeitschrift fur Kristallographie, 1972) — 1 of 2 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 4.788 | 2.712 | 2.862 | 3.695 | 3.975 | 3.181 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 70.2 | 48.1 | 44.9 | 34 | 31.7 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9008211; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 3.494 g/cm³calculated from COD 9008211 |
|---|---|
| Hardness (Mohs) | 1.5-2single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 3.4-3.5 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | yellowDana, System of Mineralogy, 6th ed. (1892) |
| Luster | pearly, resinoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Cleavage | perfectDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 246.04 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | As 60.9%, S 39.1% |
Classification
| Nickel-Strunz (10th) | 2.FA.30Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 2.FA.30Wikidata (CC0) |
| Dana (8th) | 2.11.1.1Wikidata (CC0) |