Orpiment

Orpiment is a deep orange-yellow colored arsenic sulfide mineral with formula As
2S
3. It is found in volcanic fumaroles, low temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of another arsenic mineral, realgar. It takes its name from the Latin auripigmentum (aurum − gold + pigmentum − pigment) because of its deep-yellow color.