Orpiment is derived from the latin auripigmentum , or golden pigment. Its use as a dye or pigment is limited due to its instability. Over time, orpiment will deteriorate into a powder. The process takes a long time, but exposure to light will accelerate it. Specimens should be stored in dark, enclosed containers.
Color is orange-yellow to yellow.
Luster is resinous to pearly Transparency crystals are translucent to transparent. Cleavage is perfect in one direction producing flexible, non-elastic flakes. Fracture is flaky. Hardness is 1.5-2. Specific Gravity is 3.5 Streak is yellow Associated Minerals realgar , calcite , stibnite , barite and gypsum .