Formula: Cu4(SO4)(OH)6.2H2O
Hydrated sulphate containing hydroxyl, paramorph of wroewolfeite. Both minerals are monoclinic.
Specific gravity: 3.48 to 3.5
Hardness: 2½ to 3
Streak: Greenish blue
Colour: Blue, greenish-blue
Solubility: Insoluble in water. Readily soluble in acids or ammonia.

Hydrothermal environments

Langite is an uncommon but widespread secondary mineral in the oxidation zone of copper sulphide deposits; it may be of post-mine formation, and it may be altered to brochantite (HOM, Mindat). Associated minerals include wroewolfeite, posnjakite, serpierite, devilline, chalcophyllite, connellite, brochantite, malachite and gypsum (HOM).

At Kintore, Broken Hill, New South Wales, Australia, langite is found only as intergrowths with ktenasite (AJM 3.1.43).

At St-Rome-de-Tarn, Aveyron, France, langite occurs as crystals to 5 mm on baryte (Dana).

At Canaveille, Pyrenees, France, posnjakite and langite pseudomorphs after calcite have been found (KL p193).

There are two co-type localities, both in Cornwall, England, UK. One is St Just, and the other is Fowey Consols, Tywardreath and Par.

At the Driggith and Sandbed mines, Caldbeck, Cumbria, England, UK, langite is widespread as a component of crusts surrounding fragments of copper-rich ore on the dumps, associated with brochantite and linarite; it is sometimes partly replaced by brochantite (JRS 9.39-44).

At Red Gill mine, Roughton Gill, Caldbeck, Cumbria, England, UK, langite is very rare, but it has been found associated with caledonite, and separately associated with brochantite and covellite (JRS 11.29-47).

At Roughton Gill mine, Caldbeck, Cumbria, England, UK, langite is very rare, but has been found on a matrix of chalcopyrite and quartz (JRS 14.14).

At Silver Gill, Roughton Gill, Caldbeck, Cumbria, England, UK, langite crystals commonly occur with crusts of hemimorphite, and associated with cerussite, linarite, malachite, brochantite and redgillite. Many specimens of langite are partly pseudomorphed by brochantite (JRS 8(2).85-97).

At the Ward mine, about 18 miles south of Ely, Nevada, USA, langite has been found in a suite of supergene lead and copper minerals in the Caroline tunnel. The langite occurs as minute crystals which coat superficially altered chalcopyrite in a quartz gangue. Among the supergene minerals present, brochantite and cerussite are the earliest to crystallise, followed by approximately contemporaneous serpierite, langite and linarite. Langite and serpierite may be replaced by devilline (AM 49.1143-1145).

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