Zaratite is a bright emerald green nickel carbonate mineral with formula Ni3CO3(OH)4·4H2O. 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 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, during the serpentinization rocks. Hellyerite , NiCO3·6H2O, is a related mineral.
It was found originally in Galicia in 1851, and named after Spanish diplomat and dramatist Antonio Gil y Zárate