Mineral Species:  Realgar and Orpiment

Chemical Formula: AsS

Chemical Name: Arsenic Sulfide

Mineral Class: Sulfide

Mineral Notes: Realgar is a highly unstable mineral and gradually changes to a yellow powder which is Orpiment on exposure to light. It differs from other orange and red minerals by having a uniquely orange-red streak which makes for easy identification. It typically occurs in ore veins with other Sulfides, particualrly Stibnite, and Silver and Gold. Often associated with hot-spring deposits.