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, so Realgar leaves orange-red, Orpiment leaves yellow.
How to tell apart: Streak differs, so 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, so 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, 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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