Chem., Mineral.
a salt, copper sulfate, CuSO 4 ·5H 2 O, occurring naturally as large transparent, deep-blue triclinic crystals, appearing in its anhydrous state as a white powder: used chiefly as a mordant, insecticide, fungicide, and in engraving. Also called blue copperas, chalcanthite, cupric sulfate .
[ 1760-70 ]