Vitriol is the general chemical name encompassing a class of chemical compounds comprising sulfates of certain metals – originally, iron or copper. Those mineral substances were distinguished by their color, such as green vitriol for hydrated iron(II) sulfate and blue vitriol for hydrated copper(II) sulfate.
These materials were found originally as crystals formed by evaporation of groundwater that percolated through sulfide minerals and collected in pools on the floors of old mines.
