Arsenic sulfide with vivid red-orange color. Decomposes to yellow pararealgar upon prolonged light exposure. Color: Red to orange-red. Luster: Resinous to adamantine. Streak: Orange-red. Cleavage: Good in one direction. Hardness: 1.5-2. Transparency: Transparent to translucent. Crystal system: Monoclinic. Chemical formula: AsS. Specific gravity: 3.56. Formation: Forms in low-temperature hydrothermal veins and hot spring deposits, often with orpiment. Common geological settings: China, Romania, Turkey, USA Nevada ; found near volcanic fumaroles and hot springs. Common look-alikes and related entries: Cinnabar, Orpiment, Crocoite. 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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Sources, scope & corrections
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.
Editorial owner
GeoMiner
Last updated
2026-03-30T14:36:59.830417+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.
Arsenic sulfide with vivid red-orange color. Decomposes to yellow pararealgar upon prolonged light exposure.
How can you identify Realgar?
Compare several properties rather than relying on colour alone. This entry records colour: Red to orange-red; lustre: Resinous to adamantine; streak: Orange-red; Mohs hardness: 1.5-2; cleavage: Good in one direction; crystal system: Monoclinic; transparency: Transparent to translucent. Confirm an important identification with additional field tests or qualified laboratory work.
How does Realgar form?
Forms in low-temperature hydrothermal veins and hot spring deposits, often with orpiment.
Where is Realgar commonly found?
China, Romania, Turkey, USA Nevada ; found near volcanic fumaroles and hot springs.
Is Realgar 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 Realgar commonly confused with?
Realgar may be confused with Cinnabar, Orpiment, Crocoite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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