Hellyerite, NiCO₃·6 is an hydrated nickel

Nickel

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 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.

Occurrence

The environment of formation, associated only with metamorphosed

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

 ultramafic rocks, is diagnostic compared with gaspeite

Gaspeite

Gaspeite is an extremely rare nickel carbonate mineral named for the place it was first described, in the Gaspé Peninsula, Canada.Gaspeite's formula is CO3 and it is a bright green mineral. It forms massive to reniform pappillary aggregates in fractures, bottryoidal concretions in laterite or...

, another nickel carbonate which is associated with supergene

Supergene (geology)

In ore deposit geology, supergene processes or enrichment occur relatively near the surface. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary sulfide ore minerals and...

 weathering of nickel sulfides.

Hellyerite is observed forming in shear planes in serpentinite

Serpentinite

Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...

, produced by carbonation of the serpentinite. Hellyerite forms in this environment in nickel rich serpentinites, which are metamorphosed equivalents of ultramafic cumulate rocks such as peridotite

Peridotite

A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...

 and dunite

Dunite

Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group...

. Peridotite and dunite, when fresh, can contain up to ~4,000 ppm nickel within olivine

Olivine

The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....

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It was first identified in 1958 in the Old Lord Brassy mine, Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and named after Henry Hellyer

Henry Hellyer

Henry Hellyer was an English surveyor and architect who was one of the first explorers to visit the rugged interior of the north west of Tasmania, Australia and made the most comprehensive maps of the area up to that time.-Life:...

, Chief Surveyor of the Van Diemens Land Company. It is also reported from the Pafuri nickel deposit in Limpopo Province, South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

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