Copper sulfate

Copper sulfate is blue in color in its crystalline form and produces beautiful diamond shaped crystals.

The chemical formula of hydrous copper sulfate is CuSO₄.5H₂O which is often abbreviated to CuSO₄ especially when balancing chemical equations.

Hydrous means 'with water'. Each of the pairs of copper sulfate ions in the cyrstal are surrounded by five water molecules.

Technically, CuSO₄ is refers to anhydrous copper sulfate which is produced by heating blue copper sulfate. Anhydrous means "without water'. Anydrous copper sulfate is gray-white in color and readily changes back to blue color by adding water.