Iron arsenic sulfide and the most common arsenic-bearing mineral. Important indicator of gold mineralization. Color: Silver-white to steel-gray. Luster: Metallic. Streak: Dark grayish-black. Cleavage: Good in two directions. Hardness: 5.5-6. Transparency: Opaque. Crystal system: Monoclinic. Chemical formula: FeAsS. Specific gravity: 5.9-6.2. Formation: Forms in high-temperature hydrothermal veins, often associated with gold and tungsten mineralization. Common geological settings: Worldwide; England, Germany, Portugal, Bolivia; found in gold-bearing quartz veins. Common look-alikes and related entries: Pyrite, Marcasite, Löllingite. Specimen safety: Keep this arsenic-bearing specimen intact. Do not cut, grind, polish, streak, lick, heat, or use acid on it. Avoid creating or breathing dust or fumes, wash your hands with soap and water after handling, and keep it away from food, children, and pets.
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These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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GeoMiner
Last updated
2026-03-30T14:36:58.624753+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Arsenic (inorganic compounds, as As) — CDC/NIOSH. Official occupational-hazard, exposure-route, symptom, and protective-equipment information for inorganic arsenic compounds.
Iron arsenic sulfide and the most common arsenic-bearing mineral. Important indicator of gold mineralization.
How can you identify Arsenopyrite?
Compare several properties rather than relying on colour alone. This entry records colour: Silver-white to steel-gray; lustre: Metallic; streak: Dark grayish-black; Mohs hardness: 5.5-6; cleavage: Good in two directions; crystal system: Monoclinic; transparency: Opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Arsenopyrite form?
Forms in high-temperature hydrothermal veins, often associated with gold and tungsten mineralization.
Where is Arsenopyrite commonly found?
Worldwide; England, Germany, Portugal, Bolivia; found in gold-bearing quartz veins.
Is Arsenopyrite safe to handle?
Keep this arsenic-bearing specimen intact. Do not cut, grind, polish, streak, lick, heat, or use acid on it. Avoid creating or breathing dust or fumes, wash your hands with soap and water after handling, and keep it away from food, children, and pets. Avoid creating dust or using destructive tests on an unknown specimen, and follow site-specific safety procedures.
What is Arsenopyrite commonly confused with?
Arsenopyrite may be confused with Pyrite, Marcasite, Löllingite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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