Realgar (As₄S₄) is a vivid red-orange arsenic sulfide that crystallizes from low-temperature hydrothermal and volcanic fumarolic systems. It forms paired with orpiment (As₂S₃) — together they are known as the “ruby and gold of arsenic minerals.” China’s Tengchong volcanic field (Yunnan) and Shimen mining district (Hunan) are the country’s two principal sources.
Key Facts
- Mohs hardness 1.5–2 — very soft.
- Resinous to greasy luster; transparent to translucent.
- Crystals darken and crumble to powder with prolonged sunlight exposure (light-sensitive).
- Always handle with care: arsenic compound, do not ingest or breathe dust.
- Best stored in low-light conditions to preserve color.
Notable Chinese Localities
Tengchong volcanic field (Yunnan) yields vivid red prismatic crystals from active fumaroles. The Shimen Realgar Mine (Hunan) produced the world’s largest realgar specimens during the late 20th century, including museum pieces over 30 cm.
Found at these Localities
- Shimen Realgar-Orpiment Mine (石门雄黄雌黄矿)
- Tengchong Volcanic Field (腾冲火山区)
- Yunnan (云南)
- Hunan (湖南)
