Category Halide mineral Strunz classification 3.AB.10 Space group P42/nmc | Formula
(repeating unit) HgI2 Crystal system Tetragonal | |
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Crystal class Ditetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m) | ||
Coccinite is a rare mercury iodide mineral with chemical formula of HgI2, mercury(II) iodide. in addition to its discovery locality of 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.
Discovery
The discovery was announced by del Rio in the journal of the Mexico city School of Mining. The news spread by reading that journal and a direct letters of del Rio. In the subsequent years several times the discovery was mentioned. One of the earliest notes of the discovery is a translation of a letter of del Rio to Freiesleben. In 1839 it was described as lemon coloured spots in the sandstone of Casas Vijecas. This description was also given in a Spanish book printed in 1844. In 1836 a short paper was published in Comptes rendus which was the communication of Yniestra to Arago about a discovery of del Rio. In this publication the mineral sample was deposited at the school of mines by a Mr. Jose Casas Viejas from the Querétaro province and that the mineral had a red brown colour. In 1861 the book A glossary of mineralogy by Henry William Bristow states that it has been found in Casas Viejas in Mexico as reddish brown particles on mercury selenide. Shortly after in 1862 a book about chemical technology gives the only location where the mineral can be found with a Mexican region Cavas Viejas.