A natural yellow mineral form of arsenic(III) sulphide, As2S3. The name is also used for the synthetic compound, which is used as a pigment.
Geology and Earth Sciences
Sulphide, As2S3; sp. gr. 3.5; hardness 2.0; yellow or yellowish-orange; foliated or powdery aggregate; occurs in low-temperature veins and hot-spring deposits, commonly associated with realgar and stibnite.