Zaratite from Tasmania
|Crystal system||Isometric (in part amorphous)|
|Unit cell||a = 6.16 Å; Z = 1|
Zaratite is a bright emerald green and questionable nickel carbonate mineral with formula Ni3CO3(O H)4·4 H2O. 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, NiCO3·6H2O, is a related mineral.
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