Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| As Arsenic | 60.91% | |
| S Sulfur | 39.09% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
IMA Abbreviation (Whitney-Evans 2010)
Orp
→ Orpiment
As sulfide
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
⏳ Long-term Aging & Care Timeline
slow photodecompositionyears
Trigger: UV + visible light
Intervention: Slower than realgar. Yellow may pale and crystals may dust over decades. Limit light exposure.
Pronunciation
/ˈɔːrpɪmənt/
↔ OR-pih-munt
Latin auripigmentum (gold pigment)
⚠ Safety & Handling
☠toxichigh
Arsenic trisulfide — same hazard as realgar.
Handling: Same as realgar (toxicity).
☼light-sensitivemoderate
Less light-sensitive than realgar but still degrades over decades.
Handling: Dark storage preferred.
Information provided in good faith. Consult local hazmat regulations for transport and disposal. Severely hazardous specimens may require special storage cabinets.
Luster
resinous→pearly
Pearly on cleavage; bright yellow.
Diaphaneity (Transparency)
translucent
Yellow-gold translucent.
Diagnostic Field Tests
Smell test→ Garlic-arsenic smell when struck
Same diagnostic as realgar.
Light test→ Stable in light vs realgar
Less light-sensitive than realgar.
⚠ Use dilute HCl (~10%) only on inconspicuous spots; rinse promptly. Smell-tests should be brief and ventilated. Taste-test ONLY halite/sylvite — never lead, arsenic, or sulfur minerals.
Streak Test
pale yellow
Diagnostic for arsenic sulfides — pale lemon streak.
Streak = color of the powdered mineral. Drag specimen across unglazed white porcelain plate (Mohs 6.5). For minerals harder than the plate, crush a small flake into powder and observe color.
Geological Setting
Environment:
hydrothermal
Host rock:
low-temp hydrothermal, hot-spring
Companions:
Companion of realgar.
Care notesStore in dark; light-sensitive. Arsenic — wash hands after handling. Full cleaning guide →
Market availability: Rare
Sought after; limited supply. Major shows and specialist dealers only.
Collector tier: Solid Display
Reliable mid-tier display species. Easy to find in well-formed examples; broad locality diversity.
PolymorphsShares the formula
As2S3 with: Pararealgar — same chemistry, different crystal structure.Mohs 1.5–2
Vickers (~) 75 HV
Knoop (~) 85 HK
Nickel–Strunz
2.FA.30Dana
02.13.04.01Geological setting
VolcanicHydrothermal
Element composition by mass
Formula: As₂S₃ · molar mass: 246.02 g/mol
| As | 60.91% | |
| S | 39.09% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
Mohs Hardness
1.5–2
Orpiment sits at 1.5–2 on the Mohs scale — soft enough to be scratched by a fingernail.
Colors:
Streak
Pale yellow
Pale yellow
Crystal system
Monoclinic
Monoclinic
Pronunciation/ˈɔːrpɪmənt/
Type localityŠumadija, Serbia (classical)
Sulfides & SulfosaltsSulfides
TL;DR · 1 min read
Orpiment (As₂S₃) is the bright lemon-yellow to golden arsenic sulfide companion of realgar. Its name comes from Latin "auripigmentum" — gold pigment — referencing its long historical use as a pigment in painting and manuscripts.
Orpiment (As₂S₃) is the bright lemon-yellow to golden arsenic sulfide companion of realgar. Its name comes from Latin “auripigmentum” — gold pigment — referencing its long historical use as a pigment in painting and manuscripts. It forms in low-temperature hydrothermal veins, hot springs, and as a sublimation product around volcanic fumaroles, often intergrown with realgar.
Notable Chinese Localities
Tengchong (Yunnan) produces orpiment as a fumarolic deposit. Shimen Realgar Mine (Hunan) supplied the world with golden orpiment specimens during peak production decades. Twin Creeks Mine (Nevada, USA) is the modern world standard.
Cite this entry
APA
MyMineralBox Editorial Team. (2026). Orpiment. My Mineral Box. Retrieved May 23, 2026, from https://mymineralbox.com/mineral-encyclopedia/minerals/orpiment/
MLA
MyMineralBox Editorial Team. "Orpiment." My Mineral Box, 2026, https://mymineralbox.com/mineral-encyclopedia/minerals/orpiment/. Accessed May 23, 2026.
Chicago
MyMineralBox Editorial Team. "Orpiment." My Mineral Box. Last modified May 4, 2026. https://mymineralbox.com/mineral-encyclopedia/minerals/orpiment/.
BibTeX
@misc{mmb_orpiment,
author = {{MyMineralBox Editorial Team}},
title = {{Orpiment}},
year = {2026},
publisher = {My Mineral Box},
url = {https://mymineralbox.com/mineral-encyclopedia/minerals/orpiment/},
urldate = {2026-05-23}
}