Chalcanthite
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Chalcanthite is a richly colored blue-green water-soluble sulfate mineral CuSO₄·5H₂O. It is commonly found in the late-stage oxidation zones of copper deposits. Due to its ready solubility, chalcanthite is more common in arid regions. Wikipedia
Cleavage: Perfect on; interrupted on
Color: Berlin blue to sky blue, greenish blue
Crystal class: Pinacoidal (1); (same H-M symbol)
Crystal habit: Typically stalactitic, encrusted, reniform or massive. Natural crystals are rare, but are short prismatic or tabular
Crystal system: Triclinic
Formula (repeating unit): CuSO4·5H2O
Fracture: Conchoidal