A hydrated form of nickel sulphate which occurs as a secondary mineral associated with nickel ores, typically in the form of dark green crusts and tufts.
Retgersite is nickel sulphate hexahydrate, NiSO₄·6H₂O. Crystal system: tetragonal.
1940s. From the name of J. W. Retgers, Dutch chemist and crystallographer + -ite.