Flexible sulphuret of Silver

The only account we have of this mineral is given by its discoverer, the Count de Bournon; it is extremely rare, the only specimen in England is the one figured; it was found in Mr. Partsch’s cabinet of Minerals at Vienna, among the ores of Tellurium, and was brought to England with it by my son G. B. Sowerby.

The following observations are extracted from Bournon’s Catalogue:

“I am unable to bring this substance under any of the known ores of Silver, from all of which it differs wholly in its specific characters. Its colour approaches black; it is tender and easily cut by a sharp instrument; but the cut surface, without being dull, has not so brilliant a metallic lustre as that of the sulphuret of Silver. Its primitive form is a rhomboidal tetrahedral prism of 60° and 120° divisible parallel to the terminal faces with almost the same ease as Mica. When its crystals are thin, which they generally are, they are nearly as flexible as a plate of Lead of the same thickness: this property is alone sufficient to characterize in this sulphuret of Silver a new species, and from it I have named it Argent sulfure ilexible, until some other name be given to it: by this character I have been led for a long while to esteem this substance as probably a grey Tellurium from Naggiag, but the examination of it made at my request by Dr. Wollaston has done away with this opinion, as he found only Silver, Sulphur, and slight traces of Iron in it. I have met with seven modifications of the primitive crystal.”

“In general the crystals are very small, their gangue in the specimens (8 in number) which are placed in this (the Count’s) collection is a ferriferous carbonate of Lime, of either a deep pearl grey or flesh colour, mixed with grey sulphuret of Copper and Iron, and carbonate of Lime in lenticular rhomboids. I believe they are from Hungary.”

The gaugue of my specimen is similar.