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. Streak: tin-white.
- 3Read the lusterHold the specimen under a strong light. Luster: nearly metallic.
- 4Match the color rangeCompare against the expected color range: tin-white, light gray, black, lead gray, gray, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: lamellar, nodular, reniform.
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, so Native Arsenic leaves tin-white, Antimony leaves gray; luster reads nearly metallic on Native Arsenic and metallic on Antimony.
How to tell apart: Native Arsenic is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so Native Arsenic leaves tin-white, Bismuth leaves pale silver; luster reads nearly metallic on Native Arsenic and metallic on Bismuth.
How to tell apart: Native Arsenic is noticeably harder (Mohs 3.5 vs. 2); streak differs, so Native Arsenic leaves tin-white, Stibnite leaves lead-gray; luster reads nearly metallic on Native Arsenic and metallic, splendent on cleavage surfaces on Stibnite.
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
- 5.63-5.78 g/cm³
- Streak
- Tin-white
- Luster
- Nearly metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Lamellar, nodular, reniform
- Cleavage
- Perfect on {0001}, fair on {1014}
- Rarity
- Uncommon
- Uses
- Collector, Geological study
- Host rock
- In hydrothermal veins and deposits that contain other arsenic minerals; may be in Co–Ag sulfide veins
Where rockhounds find native arsenic
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey and Washington Camp, Santa Cruz Co., Arizona, USA
- Freiberg, Schneeberg, Johanngeorgenstadt, Marienberg, and Annaberg, Saxony, Germany
- Wolfsberg and St. Andreasberg, Harz Mountains, Germany
- Wieden, Black Forest, Germany
- Gabe-Gottes mine, Rauenthal, near Sainte-Marie-aux-Mines, Haut-Rhin, France
- Jáchymov (Joachimsthal), Příbram, and Cínovec (Zinnwald), Czech Republic
Field-hunting tip
Where it forms: In hydrothermal veins and deposits that contain other arsenic minerals; may be in Co–Ag sulfide veins. If you start seeing arsenolite, cinnabar, realgar in float, you are in the right ground. Typical habit: lamellar, nodular, reniform. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify native arsenic?+
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Find native arsenic on the map
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