Noun
Arsenic sesquisulphide, produced artificially as an amorphous lemonyellow powder, and occurring naturally as a yellow crystalline mineral; -- formerly called auripigment. It is used in king's yellow, in white Indian fire, and in certain technical processes, as indigo printing.
Source: Webster's dictionaryOrpiment ( As 2 S 3 ) and realgar ( As 4 S 4 ) are somewhat abundant and were formerly used as painting pigments. Source: Internet