Realgar
Realgar is an extremely rare gem and is somewhat unstable. With exposure to light, Realgar will begin to alter to a different mineral, Pararealgar, and eventually deteriorate to a powder. Fortunately, this process takes a very long time, however. Ancient Chinese carvings of Realgar still exist but are badly damaged by the deterioration. Realgar should be kept in the dark in an enclosed container and only exposed to light for brief periods. The color of Realgar is truly amazing, a very intense orangish-red, and is well worth the effort to preserve it. Because of its Arsenic content, Realgar is somewhat poisonous and should be handled carefully. It is also very, very soft with a Mohs hardness of only 1.5 – 2.0, and therefore difficult to facet.
There are only a few locations worldwide for fine Realgar crystals. One of the best-known locations is at the Shimen mine, 33 km southeast of Shimen, Hunan Province, China. Another location known for fairly large crystals is the Palomo Mine, Castrovirreyna Province, Huancavelica Department, Peru. Very fine large crystals are also found in the USA at the Getchell mine, Potosi district, Humboldt County, Nevada.
| Category: | Sulfide mineral |
| Formula: | As4S4 |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals are prismatic, to 12 cm, and striated; more commonly massive, coarse to fine granular, or as incrustations and earthy masses. |
| Twinning: | As contact twins on [100] |
| Cleavage: | [010] Good |
| Fracture: | Sectile |
| Tenacity: | Slightly brittle |
| Hardness (Mohs): | 1.5 – 2.0 |
| Density: | 3.56 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioacitve |
| Health Warning: | CAUTION: Contains Arsenic – always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. |
| Color: | Dark Red to Orange-Red |
| Transparency: | Transparent, Translucent |
| Luster: | Resinous, Greasy, Adamantine to Sub-metallic |
| Refractive Index: | 2.538 – 2.704 Biaxial ( – ) |
| Birefringence: | 0.166 (very high) |
| Dispersion: | Very Strong; r > v |
| Pleochroism: | Visible; nearly colorless to pale golden yellow |
| Anisotropism: | Strong |
