User:Arccc/Orpiment
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Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with the formula As
2S
3. It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of another arsenic sulfide mineral, realgar. Orpiment takes its name from the Latin auripigmentum (aurum, "gold" + pigmentum, "pigment") because of its deep-yellow color. Orpiment is widely used in ancient artistic creations, medical, and other fields. Orpiment is toxic and hard to conserve, and is no longer commonly used in contemporary time.
Quick Facts Orpiment, General ...
Orpiment | |
---|---|
General | |
Category | Sulfide mineral |
Formula (repeating unit) | As2S3 |
IMA symbol | Orp[1] |
Strunz classification | 2.FA.30 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/n |
Unit cell | a = 11.475(5), b = 9.577(4) c = 4.256(2) [Å], β = 90.45(5)°; Z = 4 |
Identification | |
Color | Lemon-yellow to golden or brownish yellow |
Crystal habit | Commonly in foliated columnar or fibrous aggregates; may be reniform or botryoidal; also granular or powdery; rarely as prismatic crystals |
Twinning | On {100} |
Cleavage | Perfect on {010}, imperfect on {100}; |
Tenacity | Sectile |
Mohs scale hardness | 1.5–2 |
Luster | Resinous, pearly on cleavage surface |
Streak | Pale lemon-yellow |
Diaphaneity | Transparent |
Specific gravity | 3.49 |
Optical properties | Biaxial (−) |
Refractive index | nα = 2.400 nβ = 2.810 nγ = 3.020 |
Birefringence | δ = 0.620 |
Pleochroism | In reflected light, strong, white to pale gray with reddish tint; in transmitted light, Y = yellow, Z = greenish yellow |
2V angle | Measured: 30° to 76°, Calculated: 62° |
Dispersion | r > v, strong |
References | [2][3][4] |
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