Coccinite | |
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![]() Coccinite, from Backofen Mine, Rhineland-Palatinate, Germany | |
General | |
Category | Halide mineral |
Formula (repeating unit) | HgI2 |
IMA symbol | Cci[1] |
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 | [2][3][4] |
Coccinite is a rare mercury iodide mineral with chemical formula of HgI2, mercury(II) iodide.[5][6] It was first discovered in Casas Viejas, Mexico;[7] 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.[2] At the Thuringia deposit the mineral occurs as a sublimation product resulting from fires associated with pyrite-bearing graptolitic slate.[6]