Native arsenic is a brittle, metallic mineral that typically occurs in reniform or botryoidal masses with a characteristic tin-white color that quickly tarnishes to a dull grey or black. It is primarily found in hydrothermal vein deposits alongside other arsenic sulfides and silver minerals. Due to its high toxicity, collectors should handle samples with caution and store them in sealed containers.
Is this arsenic?
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 arsenic with a known reference. Arsenic sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Arsenic leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Arsenic typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: tin-white, gray, black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: reniform, botryoidal, massive, or granular aggregates.
Often confused with
Arsenic vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Arsenic leaves black, Antimony leaves tin-white.
How to tell apart: Arsenic is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs — Arsenic leaves black, Bismuth leaves silver-white.
How to tell apart: Arsenopyrite is the harder of the two (Mohs 5.5-6 vs. 3.5).
Often found alongside arsenic
Minerals reported to co-occur with arsenic. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- As
- Mohs hardness
- 3.5
- Density
- 5.7-5.8 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Reniform, Botryoidal, Massive, Or Granular Aggregates
- Cleavage
- Perfect On {0001}
- Rarity
- Uncommon
- Uses
- Collector, Specimen
- Host rock
- Hydrothermal Veins
- Typical price
- $20-200 thumbnail, $100-500+ cabinet
Where rockhounds find arsenic
6 mapped spotsClassic worldwide localities
- Andreasberg, Germany
- Jáchymov, Czech Republic
- Kongsberg, Norway
- Chañarcillo, Chile
- Sterling Hill, USA
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where arsenic typically forms. If you start seeing realgar, orpiment, proustite in float, you are in the right ground. Field specimens usually show a reniform, botryoidal, massive, or granular aggregates habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Nevada, Alabama, Montana — start trip planning there.
Common questions
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Find arsenic on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
