Mineral Species: Orpiment

Chemical Formula: As2S3

Chemical Name: Arsenic Sulphide

Mineral Class: Sulphide

Mineral Notes: Orpiment is a rather rare mineral, but is nevertheless an important ore of Arsenic. Like Cinnabar and Stibnite, it is a late magmatic mineral, associated with low temperature hydrothermal springs. It is commonly formed by alteration of other Arsenic minerals which decompose on exposure to light. Its yelow colour contrasts stongly with the closely related red-coloured Realgar. The only other common yellow mineral found in similar environments is Sulfur, which lacks Orpiment's perfect cleavage flexible cleavage flakes. 

Description: A large specimen of solid Orpiment. Numerous crystals are present and easily seen on the surface by their individual crystal faces. The colour is a very strong canary-yellow and together with a strong waxy luster make this a very attractive specimen.

Location: Getchell Mine, Adam Peak, Potosi District, Humboldt Co., Nevada, USA.