Orpiment
ID: 66
Orpiment
Chemical Formula
As₂S₃
Hardness (Mohs)
1.5 - 2
Crystal System
Monoclinic
Streak
Pale yellow
Luster
Resinous, pearly on cleavage surfaces
Diaphaneity
Translucent
Color
Lemon-yellow to brownish-yellow
Crystal Habit / Mode of Occurrence
Typically foliated or massive, also as short prismatic or tabular crystals, often curved or distorted. Can also be found as coatings.
Fun Facts
Orpiment is highly toxic due to its arsenic content and was historically used as a pigment, despite the dangers. Its name comes from the Latin "auripigmentum," meaning "golden pigment."