Realgar is a striking, bright red to orange mineral often found alongside yellow orpiment in hydrothermal deposits. Due to its extreme sensitivity to light, it will eventually decompose into a powdery yellow substance if left exposed, making dark storage essential for preservation.
Is this realgar?
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 realgar with a known reference. Realgar 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. Realgar leaves a orange-red streak.
- 3Read the lusterHold the specimen under a strong light. Realgar typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: red, orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: short prismatic crystals, granular, massive.
Often confused with
Realgar vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Realgar leaves orange-red, Orpiment leaves yellow.
How to tell apart: Streak differs — Realgar leaves orange-red, Cinnabar leaves scarlet; luster reads resinous on Realgar and adamantine on Cinnabar.
How to tell apart: Vanadinite is the harder of the two (Mohs 3 vs. 1.5-2); streak differs — Realgar leaves orange-red, Vanadinite leaves white.
Often found alongside realgar
Minerals reported to co-occur with realgar. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- As₄S₄
- Mohs hardness
- 1.5-2
- Density
- 3.5-3.6 g/cm³
- Streak
- Orange-red
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Short Prismatic Crystals, Granular, Massive
- Cleavage
- Distinct Basal
- Rarity
- Uncommon
- Uses
- Collector, Pigment (historical)
- Host rock
- Hydrothermal Veins
- Typical price
- $10-100 thumbnail, $50-500 cabinet
Where rockhounds find realgar
4 mapped spotsClassic worldwide localities
- Tajikistan
- China
- Peru
- Romania
- USA
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where realgar typically forms. If you start seeing orpiment, calcite, stibnite in float, you are in the right ground. Field specimens usually show a short prismatic crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Washington, Wyoming — start trip planning there.
Common questions
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Find realgar on the map
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