This proustite/pyrargyrite is from Mineral County, Colorado. The mines in this area are mostly load claims that produced silver, gold, lead, copper and zinc.The label for this specimen simply says “Ruby Silver – Colorado”. It was part of an older collection of minerals from Mineral County Colorado. This designation would put it in the silver sulfate series of minerals. However, the exact classification cannot be determined without laboratory analysis. Proustite contains the elements Ag, As, S and pyrargyrite contains the elements Ag, Sb, S. This piece consists of a naturally cleaved crystalline proustite with minor pyrite (seen on rear surface photo 4) and acanthite. This specimen measures 7/8 x 11/16 x 5/16 inches or 22 x 18 x 8 mm.