Wendy & Frank Melanson Collection An exceptional specimen of argentite from one of the world’s most famous silver districts. As with all specimens of Ag2S, the true crystal form at ambient temperature is monoclinic, making this a polymorph of Acanthite after argentite. Argentite is only stable above temperatures of 179 degrees C, and heating Acanthite above this temperature converts it to argentite. In this specimen, the original isometric crystals of argentite are remarkably well preserved- an exceptional specimen from a world-class locale. Previously in the George Robinson collection.