What is "langite"

n. (context mineralogy English) A monoclinic-domatic mineral containing copper, hydrogen, oxygen, and sulfur.

Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, England. It is dimorphous with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang (1838–1921), who was Professor of Physics at the University of Vienna, Austria.