Langite (image width: 5 mm) Locality: mining waste tip of Richtarova near Stare Hory, Špania Dolina, 10 km northwords of Banská Bystrica, Slovakia — Photo: Joachim Esche · CC BY-SA 3.0 de
Langite
A rare hydrated copper sulfate-hydroxide forming druses of small blue-green crystals where copper sulfides oxidize — first described from Cornwall.
Intro adapted from Wikipedia (CC BY-SA).
Langite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Cu₄(SO₄)(OH)₆·2H₂O.
It crystallizes in the monoclinic crystal system (space group Pc).
Key properties: Mohs hardness 2.5–3; specific gravity 3.28–3.34; Vitreous to silky luster; refractive index 1.755; optically biaxial.
IMA symbol Lgt, grandfathered status — known before the IMA’s founding, named in 1864.
An uncommon but widespread secondary mineral in the oxidation zone of copper sulfide deposits; may be of post-mine formation.
It is found associated with Wroewolfeite, posnjakite, serpierite, devilline, chalcophyllite, connellite, brochantite, malachite, gypsum.
The mineral was named to honor Victor von Lang (1838–1921), physicist and crystallographer, Professor of Physics, University of Vienna, Vienna, Austria.