Zaratite is a bright emerald green nickel carbonate mineral with formula Ni<sub>3</sub>CO<sub>3</sub>(OH)<sub>4</sub>÷4H<sub>2</sub>O. Zaratite crystallizes in the isometric crystal system as massive to mammillary encrustations and vein fillings. It has a specific gravity of 2.6 and a Mohs hardness of 3 to 3.5. It has no cleavage and is brittle to conchoidal fracture. The luster is vitreous to greasy.
It is a rare secondary mineral formed by hydration or alteration of the primary nickel and iron bearing minerals, chromite, pentlandite, pyrrhotite, and millerite, during the serpentinization of ultramafic rocks. Hellyerite, NiCO<sub>3</sub>÷6H<sub>2</sub>O, is a related mineral. It was found originally in Manolita mine, Teixedelo, Cedeira, La Coruña province, Galicia, Spain in 1851, and named after Spanish diplomat and dramatist Antonio Gil y Zárate (1793âÂÂ1861).