Properties
| Category | Sulfide mineral |
|---|---|
| Formula | As4S4 or AsS |
| Crystal system | Monoclinic |
| Color | Red to yellow-orange; in polished section, pale gray, with abundant yellow to red internal reflections |
| Crystal habit | Prismatic striated crystals; more commonly massive, coarse to fine granular, or as incrustations |
| Cleavage | Good on {010}; less so on {101}, {100}, {120}, and {110} |
| Tenacity | Sectile, slightly brittle |
| Mohs scale hardness | 1.5–2 |
| Luster | Resinous to greasy |
| Streak | Red-orange to red |
| Diaphaneity | Transparent |
| Specific gravity | 3.56 |
From the Wikipedia article
Realgar, also known as arsenic blende, ruby sulphur or ruby of arsenic, is an arsenic sulfide mineral with the chemical formula α-As4S4. It is a soft mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment. It is orange-red in color, and burns with a bluish flame releasing fumes of arsenic and sulfur. It is trimorphous with pararealgar and bonazziite.
Source
Source record: crystal-compendium/realgar/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Realgar — revision id 1370050502. Text and properties from Wikipedia, licensed CC BY-SA 4.0.