Argentopyrite
Argentopyrite is a moderately rare sulfide mineral with the chemical formula AgFe2S3. It is one of the natural compounds of the MFe2S3 type, with M being caesium in very rare pautovite, copper in relatively common cubanite, potassium in rare rasvumite and thallium in rare picotpaulite. The type locality is Jáchymov in Czech Republic. Chemically similar mineral include sternbergite (dimorphous with argentopyrite), lenaite, AgFeS2, and argentopentlandite, Ag(Fe,Ni)8S8.[2]