smithite

Century Dictionary and Cyclopedia

1. n. A rare mineral species from the dolomite of the Binnenthal, Switzerland. It occurs in light-red monoclinic crystals with adamantine luster, and contains sulphur, arsenic, and silver. Its formula is prooably AgAsS₂.

Wiktionary

1. n. mineralogy A monoclinic-prismatic mineral containing arsenic, silver, and sulfur.