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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:

Realgar · Cinnabar · Calcite

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.

Often found withRealgar · Stibnite · Cinnabar

Mohs 1.5–2

Vickers (~) 75 HV

Knoop (~) 85 HK

Nickel–Strunz 2.FA.30

Dana 02.13.04.01

Geological 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

1
Talc 2
Gypsum 3
Calcite 4
Fluorite 5
Apatite 6
Orthoclase 7
Quartz 8
Topaz 9
Corundum 10
Diamond

Orpiment sits at 1.5–2 on the Mohs scale — soft enough to be scratched by a fingernail.

Colors:

Streak
Pale yellow

Crystal system
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}
}