Chalcanthite - CuSO₄·5H₂O

Habit: Dark blue to sky blue or greenish blue. Uncommonly short prismatic to thick tabular crystals; commonly stalactitic to reniform crusts, cross-vein fibrous, massive or granular. Vitreous to resinous luster; translucent. White streak.

Environment: A secondary mineral in the oxidized portions of copper sulfide deposits, commonly of post-mining formation; found rarely as a fumarolic deposit.

Etymology: From chalcanthum, its old Latin name, which means "flowers of copper."

Chalcanthite is used as an ore of copper.