Orpiment is a distinctively bright yellow arsenic sulfide mineral often found associated with realgar in hydrothermal veins. It typically forms massive, foliated, or powdery masses and is highly prized by collectors for its vivid color, though its softness and toxicity require careful handling.
Is this anorpiment?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch anorpiment with a known reference. Anorpiment sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Anorpiment leaves a lemon yellow streak.
- 3Read the lusterHold the specimen under a strong light. Anorpiment typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, foliated, or powdery coatings.
Often confused with
Anorpiment vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Anorpiment leaves lemon yellow, Realgar leaves orange-red.
How to tell apart: Streak differs — Anorpiment leaves lemon yellow, Sulfur leaves white.
How to tell apart: Greenockite is the harder of the two (Mohs 3-3.5 vs. 1.5-2); streak differs — Anorpiment leaves lemon yellow, Greenockite leaves brick-red to orange-yellow; luster reads resinous on Anorpiment and adamantine to resinous on Greenockite.
Often found alongside anorpiment
Minerals reported to co-occur with anorpiment. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- As₂S₃
- Mohs hardness
- 1.5-2
- Density
- 3.4-3.5 g/cm³
- Streak
- Lemon Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Foliated, Or Powdery Coatings
- Cleavage
- Perfect in One Direction
- Rarity
- Common
- Uses
- Collector, Pigment (historical), Industrial (arsenic Source)
- Host rock
- Low-temperature Hydrothermal Veins and Fumaroles
- Typical price
- $10-100 per specimen
Where rockhounds find anorpiment
Classic worldwide localities
- El'brusskiy, Russia
- Quiruvilca, Peru
- Bor, Serbia
- Twin Creeks Mine, USA
Field-hunting tip
Look in low-temperature hydrothermal veins and fumaroles country — that is the host setting where anorpiment typically forms. If you start seeing realgar, calcite, stibnite in float, you are in the right ground. Field specimens usually show a massive, foliated, or powdery coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find anorpiment on the map
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