Orpiment (arsenic sulphide) forms soft, heavy, fragile crystals with a greasy lustre. It fuses easily, giving off arsenic fumes with a strong garlic smell that conceal fumes of sulphur dioxide. The mineral is deposited by hot springs but is also found around fumaroles, metamorphic dolomites and in low-temperature hydrothermal veins associated with realgar and native arsenic. Orpiment is used to remove hair in the tanning of hides and as a source of arsenic. In the 19th century it was used by artists as a pigment. This sample is from Arizona, USA.