The Probert Encyclopaedia of Rocks & Minerals

ORPIMENT

Orpiment is a secondary mineral with the formulae As2S3 and a relative hardness of 2. It is a rare mineral usually associated with realgar. Orpiment is an important source of industrial arsenic and is used in dyeing. Orpiment can be distinguished from sulphur by its perfect cleavage, and strong smell of garlic (arsenic) when heated.
Research Orpiment