In nature, dimorphite forms primarily by deposition in volcanic fumaroles at temperatures of 70–80 °C (158–176 °F).
Dimorphite was first discovered in such a fumarole near Naples, Italy in 1849 by the mineralogist Arcangelo Scacchi (1810–1893).
[5] Since its discovery, dimorphite has been found in the Alacrán silver mine near Copiapó, Chile.
[3] It has also been reported from Cerro de Pasco, Peru, and the Lavrion District Mines in Attica, Greece.
[6] Dimorphite can be synthesized by melting arsenic and sulfur together in the proper molar ratios in vacuum.