Orpiment is a soft, highly distinctive yellow arsenic sulfide mineral often found alongside realgar. Collectors prize its bright color and foliated or bladed crystal habits, though it is sensitive to light and should be stored in a closed, dark container to prevent degradation.
Is this orpiment?
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 orpiment with a known reference. Orpiment 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. Orpiment leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Orpiment typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange, brownish-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: foliated, columnar, granular, or massive.
Often confused with
Orpiment vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside orpiment
Minerals reported to co-occur with orpiment. 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
- 3.48 g/cm³
- Streak
- Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Foliated, Columnar, Granular, Or Massive
- Cleavage
- Perfect in One Direction
- Rarity
- Common
- Uses
- Collector, Historical Pigment
- Host rock
- Hydrothermal Veins, Volcanic Fumaroles, And Hot Spring Deposits
- Typical price
- $10-150 depending on specimen size and clarity
Where rockhounds find orpiment
4 mapped spotsClassic worldwide localities
- Bulong, Australia
- El'brusskiy, Russia
- Quiruvilca, Peru
- Twin Creeks Mine, USA
Field-hunting tip
Look in hydrothermal veins, volcanic fumaroles, and hot spring deposits country — that is the host setting where orpiment typically forms. If you start seeing realgar, stibnite, calcite in float, you are in the right ground. Field specimens usually show a foliated, columnar, granular, or massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Wyoming — start trip planning there.
Common questions
How do you identify orpiment?+
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Find orpiment on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
