Chalcanthite

sulphate

chalcopyrite

Formula: Cu(SO4).5H2O sulphate
Specific gravity: 2.2 to 2.3
Hardness: 2Æ
Streak: Blue
Colour: Blue
Solubility: Readily soluble in water, hydrochloric, sulphuric and nitric acid
Environments:

Hydrothermal environments

Chalcanthite is a secondary mineral that is found in the oxidation zone of copper deposits. It forms only in conditions of low pH (very acid) and high sulphate concentration, which occur only in exceptionally arid conditions; normally copper and sulphate ions remain in solution. Chalcanthite is formed by the oxidation of chalcopyrite and other copper sulphates. It is often found as a post-mining deposit on mine walls, where it crystallises from mine waters. When the carbonate concentration is similar to the atmospheric value, at successively higher values of pH (more alkaline conditions), chalcanthite is replaced by antlerite then brochantite then malachite (JRS 18.12, 13).

Common impurities: Fe,Mg,Co

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