Native arsenic is a brittle metallic mineral that frequently tarnishes to a dull dark gray or black when exposed to air. It typically occurs in massive, botryoidal, or reniform habits and is most commonly found in hydrothermal veins associated with silver and other arsenic-bearing sulfides.
Is this native 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 native arsenic with a known reference. Native 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. Native Arsenic leaves a tin-white to gray streak.
- 3Read the lusterHold the specimen under a strong light. Native Arsenic typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: tin-white, light gray, black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: reniform, botryoidal, massive, or granular.
Often confused with
Native Arsenic vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Native Arsenic leaves tin-white to gray, Antimony leaves tin-white.
How to tell apart: Native Arsenic is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs — Native Arsenic leaves tin-white to gray, Bismuth leaves silver-white.
How to tell apart: Native Arsenic is noticeably harder (Mohs 3.5 vs. 2); streak differs — Native Arsenic leaves tin-white to gray, Stibnite leaves lead-gray.
Often found alongside native arsenic
Minerals reported to co-occur with native 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
- Colors
- Streak
- Tin-white to Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Reniform, Botryoidal, Massive, Or Granular
- Cleavage
- Perfect On {0001}
- Rarity
- Uncommon
- Uses
- Collector, Geological Study
- Host rock
- Hydrothermal Veins
- Typical price
- $20-150 thumbnail, $200-800 cabinet
Where rockhounds find native arsenic
Classic worldwide localities
- Ste-Marie-aux-Mines, France
- Andreasberg, Germany
- Kongsberg, Norway
- Eureka, Utah, USA
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where native arsenic typically forms. If you start seeing arsenopyrite, proustite, realgar in float, you are in the right ground. Field specimens usually show a reniform, botryoidal, massive, or granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find native arsenic on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
