realgar

noun

1. arsenic disulfide, As2S2, found in nature as an orange-red mineral and also produced artificially: used in pyrotechnics.

noun

1. a rare orange-red soft mineral consisting of arsenic sulphide in monoclinic crystalline form. It occurs in Utah and Romania and as a deposit from hot springs. It is an important ore of arsenic and is also used as a pigment. Formula: AsS