Hellyerite, NiCO3·6(H2O), is a hydrated nickel carbonate mineral. It is light blue to bright green in colour, has a hardness of 2.5, a vitreous luster, a white streak and crystallises in the monoclinic system. The crystal habit is as platy and mammillary encrustations on its matrix. It is a pentahydrate according to X-ray crystallography. The solid consists of [Ni2(CO3)2(H2O)8] subunits with an extra pair of water of hydration.
Hellyerite, NiCO3·6(H2O), is a hydrated nickel carbonate mineral. It is light blue to bright green in colour, has a hardness of 2.5, a vitreous luster, a white streak and crystallises in the monoclinic system. The crystal habit is as platy and mammillary encrustations on its matrix. It is a pentahydrate according to X-ray crystallography. The solid consists of [Ni2(CO3)2(H2O)8] subunits with an extra pair of water of hydration.
==Occurrence== The environment of formation, associated only with metamorphosed ultramafic rocks, is diagnostic compared with gaspeite, another nickel carbonate which is associated with supergene weathering of nickel sulfides.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).