What is Langite?
Langite is a vivid blue-green hydrated copper sulfate from oxidised ore deposits, often forming delicate coatings and small tabular crystals.
Mineralogy and crystal structure
Reference formula: Cu4SO4(OH)6·2H2O. Langite is a monoclinic hydrated copper sulfate hydroxide and commonly occurs with brochantite, posnjakite, devilline and other secondary copper minerals. Its hydration and fine-grained habit make moisture and surface preservation important. Langite is classified with sulfates and has a monoclinic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.9–4.0.
Colour, lustre and habit
Typical colours include blue, blue-green, green. The usual tabular, fibrous, crusty habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Langite forms in or is associated with oxidised copper sulfide deposits and sulfate-rich mine environments. Important documented localities include the United Kingdom, France, Germany, Greece, Chile and Australia.
Blue-green chemistry on a mine wall
Langite turns a thin crust into a collector story. Its blue-green colour and delicate habit show how oxygenated water transforms primary copper ores, especially when the specimen preserves several related sulfate minerals together.
Collecting and care
Soft and moisture-sensitive: avoid washing, acids and abrasion, and keep labelled as a copper-bearing sulfate.
