Overview
Chalcanthite is natural, water-soluble copper sulphate pentahydrate. It is a secondary mineral that is formed in arid climates or in rapidly oxidizing copper deposits. It is usually of post-mining formation, forming on mine walls and by the action of acidic surface waters on veins of copper ore.
CAUTION: Many, usually well-crystallised chalcanthite specimens offered for sale (e.g. on-line auctions), are artificially grown.
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Formula
CuSO4 5H2O
Colour
Green, green blue, light blue, or dark blue; colourless to pale blue in transmitted light.
Hardness
2½
Specific Gravity
2.286
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