This remarkable towering cluster of acanthite (pseudomorph after argentite) features a crystal 2.8 cm in height. The main crystals are sharp. The specimen is a floater, but the backside is roughly-developed. A minor interesting feature of this specimen visible with magnification is on one face of the large crystal – there are small growths showing the form of truncated stumps of wire silver, which appear to have been partially or entirely replaced by a second generation of acanthite. However, it’s the sharp large crystal on this one that makes it such a great acanthite specimen.
About These Acanthites
Well-crystallized acanthite has never been common and most of the known localities for crystals are historic, making it difficult, and usually expensive, to obtain fine specimens. The finds at Imiter (Africa’s largest silver mine) in recent years have placed Imiter among the world’s best localities for crystallized acanthite. Although these crystals formed as argentite, argentite is not stable below 179C, at which point it changes to monoclinic acanthite. The specimens are acanthite pseudomorphs after argentite, retaining the isometric crystal form of the original argentite crystals. I assembled this lot of acanthites over a period of about two years. Most of these specimens, from the 2008 find, remained in Morocco until 2013.