Realgar / Orpiment super rare mineral from Russia. (Altai mountains / Siberia)

The mineral orpiment or auripigment is an arsenic sulfide with the chemical formula As2S3. The transparent to translucent lemon yellow, orange yellow or brown yellow orpiment has a pearly luster, a pale yellow stripe color and the mineral has a perfect cleavage according to the crystal plane [010]. The crystal system is monoclinic. Orpiment has an average density of 3.52, the hardness is 1.5 to 2 and the mineral is not radioactive. The mineral is strongly pleochroic, from white to gray-white with a light red tint. The name of the mineral auripigment is derived from the Latin aurus (gold) and pigmentum (dye), because of the golden luster of the mineral. As a yellow dye it was also known as operment, yellow sulfur arsenic, rus yellow, Chinese yellow or king's yellow. Orpiment is a mineral formed in low-temperature hydrothermal veins, in hot springs, and as a weathering product of arsenic-bearing minerals, chiefly realgar. The type locality is not defined. The mineral is found, among other places, in the Twin Creeks Mine, north of Winnemucca, Humboldt County, Nevada, United States.