Diamond Brand® Moist Ferrous Sulfate Heptahydrate, also referred to as Moist Copperas, is the moist or wet crystalline form of Ferrous Sulfate containing ~8% exterior or free water ([FeSO₄•7H₂O]H₂O) and ~44% interior water. It is derived from the processing of ilmenite ore in the manufacturing of the paint pigment Titanium Dioxide, or as a co-product from the pickling of steel.