chalcanthite

Chalcanthite is a mineral comprising copper sulfate pentahydrate, CuSO4·5H2O. It forms vivid blue, transparent crystals and is highly soluble in water. In hand samples it commonly appears as deep blue crystals or crusts on rock surfaces, and in larger specimens may display prismatic or tabular habit. The mineral crystallizes in the monoclinic system.

Chalcanthite occurs in the oxidized zones of copper sulfide deposits and in arid, evaporitic environments where copper-bearing fluids precipitate copper sulfate as solutions concentrate. It is frequently found in the vicinity of other secondary copper minerals such as malachite or azurite and can form as efflorescences on mine walls or in cave deposits.

Physically, chalcanthite is blue to azure, highly transparent to translucent, with a vitreous luster. It is soluble in water, readily dissolving to give blue solutions. Upon heating, it loses water, converting toward anhydrous copper sulfate.

Historically, chalcanthite is also known as blue vitriol and served as a source of copper and as a laboratory reagent. It finds limited use today due to its solubility and toxicity; it is primarily collected by mineral enthusiasts and studied as a chemical specimen. The mineral is toxic if ingested and can be hazardous if inhaled or absorbed through the skin, and should be handled with care and proper disposal measures.