Coccinite
| Coccinite | |
|---|---|
Coccinite, from Backofen Mine, Rhineland-Palatinate, Germany | |
| General | |
| Category | Halide mineral |
| Formula | HgI2 |
| IMA symbol | Cci |
| Strunz classification | 3.AB.10 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | P42/nmc |
| Unit cell | a = 4.376 Å, c = 12.41 Å, Z = 2 |
| Identification | |
| Colour | Orange-red |
| Cleavage | Good on {001} |
| Mohs scale hardness | 2 |
| Streak | Orange |
| Diaphaneity | Translucent |
| Specific gravity | 3.17 (calculated) |
| Optical properties | Uniaxial (-) |
| Refractive index | 2.684 (avg) |
| Birefringence | 0.193 |
| Other characteristics | Volatile at room temperature, toxic |
| References | |
Coccinite is a rare mercury iodide mineral with chemical formula of HgI2, mercury(II) iodide. It was first discovered in Casas Viejas, Mexico; it has also been reported from Broken Hill, New South Wales, and from a uranium mine in Thuringia and old mercury workings in the Rhineland-Palatinate in Germany. At the Thuringia deposit the mineral occurs as a sublimation product resulting from fires associated with pyrite-bearing graptolitic slate.