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. Streak: red-orange to red.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to greasy.
- 4Match the color rangeCompare against the expected color range: red, orange, aurora red, orange yellow, dark red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: druse, massive, prismatic.
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 red-orange to red, Orpiment leaves pale lemon-yellow.
How to tell apart: Streak differs, so Realgar leaves red-orange to red, Cinnabar leaves scarlet; luster reads resinous to greasy on Realgar and adamantine, inclining to metallic when dark; dull in friable material on Cinnabar.
How to tell apart: Streak differs, so Realgar leaves red-orange to red, Vanadinite leaves white to pale red or pale yellow; luster reads resinous to greasy on Realgar and subresinous to subadamantine on Vanadinite.
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
- 3.56 g/cm³
- Colors
- Streak
- Red-orange to red
- Luster
- Resinous to greasy
- Transparency
- Transparent when fresh
- Crystal system
- Monoclinic
- Crystal habit
- Druse, massive, prismatic
- Cleavage
- Good on {010}; less so on {101}, {100}, {120}, and {110}
- Rarity
- Uncommon
- Uses
- Collector, Pigment (historical)
- Host rock
- Most commonly as a low-temperature hydrothermal vein mineral associated with As–Sb minerals; also as volcanic sublimations and in hot spring deposits; in carbonate and clay sedimentary rocks
Where rockhounds find realgar
4 mapped spotsClassic worldwide localities
- Getchell mine, Potosi district, Humboldt Co., Nevada, USA
- Tooele Co., Utah, at Mercur, USA
- Monte Cristo district, Snohomish Co., and in the Royal Reward mine, in the Green River Gorge, King Co, Washington, USA
- Schneeberg, Saxony, and at St. Andreasberg, Harz Mountains, Germany
- Lengenbach quarry, Binntal, Valais, Switzerland
- Baia Sprie (Felsőbánya), Cavnic (Kapnikbánya), and at Săcărı̂mb (Nagyág), Romania
Field-hunting tip
Where it forms: Most commonly as a low-temperature hydrothermal vein mineral associated with As–Sb minerals; also as volcanic sublimations and in hot spring deposits; in carbonate and clay sedimentary rocks. If you start seeing orpiment, arsenolite, calcite in float, you are in the right ground. Typical habit: druse, massive, prismatic. 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
How do you identify realgar?+
Where is realgar found?+
Can I find realgar in the United States?+
Is realgar safe to handle?+
What rocks look like realgar?+
What minerals are found with realgar?+
What kind of rock does realgar form in?+
What is realgar used for?+
Find realgar on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
