Dimorphite (chemical name tetraarsenic trisulfide) is a very rare orange-yellow chalcogenide mineral. In nature, dimorphite forms primarily by deposit in volcanic fumaroles at temperatures of 70°-80°C (158°F-176°F). Dimorphite was first discovered in a such a fumarole near Naples, Italy in 1849 by the mineralologist Arcangelo Scacchi (1810-1893). Since its discovery, dimorphite has been found in the Alacrán silver mine near Copiapó, Chile. It has also been reported from Cerro de Pasco, Peru, and the Lavrion District Mines in Attica, Greece.