Nickel(II) sulfate is a bluish solid. It dissolves in water. It is normally attached to some water molecules (hydrated). When it is anhydrous (not attached to water molecules), it is yellow. It reacts with bases to make nickel(II) hydroxide.
Nickel(II) sulfate is used to make other nickel compounds. It is also used in the electroplating of nickel on metal objects. It is used in the lab.