# Hellyerite

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Carbonate mineral

Hellyerite Zaratite (emerald-green coating), hellyerite (powder-blue) and heazlewoodite (light bronze) General Category Carbonate mineral Formula NiCO3·5.5(H2O) IMA symbol Hy[1] Strunz classification 5.CA.20 Crystal system Monoclinic Crystal class Prismatic (2/m) (same H-M symbol) Space group C2/c Unit cell a = 10.77, b = 7.29 c = 18.68 [Å]; β = 94°: Z = 8 Identification Color Pale blue Crystal habit As crystal fragments and microcrystalline coatings Twinning Fine lamellar parallel to cleavage Cleavage One perfect, two good at 112° to each other and perpendicular to the perfect cleavage Mohs scale hardness 2.5 Luster Vitreous Diaphaneity Semitransparent Specific gravity 1.97 Optical properties Biaxial (−) Refractive index nα = 1.455 nβ = 1.503 nγ = 1.549 Birefringence δ = 0.094 Pleochroism X = Y = very pale greenish blue; Z = pale greenish blue 2V angle Measured: 85° Alters to Decomposes on air exposure References [2][3][4]

**Hellyerite**, NiCO3·6(H2O), is a hydrated [nickel](/source/Nickel) [carbonate mineral](/source/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](/source/Monoclinic) system. The crystal habit is as platy and mammillary encrustations on its matrix. It is a pentahydrate according to [X-ray crystallography](/source/X-ray_crystallography). The solid consists of [Ni2(CO3)2(H2O)8] subunits with an extra pair of [water of hydration](/source/Water_of_hydration).[5]

## Occurrence

The environment of formation, associated only with [metamorphosed](/source/Metamorphism) [ultramafic](/source/Ultramafic) rocks, is diagnostic compared with [gaspeite](/source/Gaspeite), another nickel carbonate which is associated with [supergene](/source/Supergene_(geology)) weathering of nickel [sulfides](/source/Sulfide_minerals).

Hellyerite is observed forming in [shear planes](/source/Shear_(geology)) in [serpentinite](/source/Serpentinite), produced by carbonation of the serpentinite. Hellyerite forms in this environment in nickel rich serpentinites, which are metamorphosed equivalents of ultramafic [cumulate rocks](/source/Cumulate_rocks) such as [peridotite](/source/Peridotite) and [dunite](/source/Dunite). Peridotite and dunite, when fresh, can contain up to ~4,000 ppm nickel within [olivine](/source/Olivine).

It was first identified in 1958 in the Old Lord Brassy mine,[6] [Tasmania](/source/Tasmania), [Australia](/source/Australia) and named after [Henry Hellyer](/source/Henry_Hellyer) (1791–1832), Chief Surveyor of the [Van Diemens Land](/source/Van_Diemens_Land) Company.[3] It is also reported from the Pafuri nickel deposit in [Limpopo Province](/source/Limpopo_Province), [South Africa](/source/South_Africa).[4]

## References

1. **[^](#cite_ref-1)** Warr, L.N. (2021). ["IMA–CNMNC approved mineral symbols"](https://doi.org/10.1180%2Fmgm.2021.43). *Mineralogical Magazine*. **85** (3): 291–320. [Bibcode](/source/Bibcode_(identifier)):[2021MinM...85..291W](https://ui.adsabs.harvard.edu/abs/2021MinM...85..291W). [doi](/source/Doi_(identifier)):[10.1180/mgm.2021.43](https://doi.org/10.1180%2Fmgm.2021.43). [S2CID](/source/S2CID_(identifier)) [235729616](https://api.semanticscholar.org/CorpusID:235729616).

1. **[^](#cite_ref-Webmin_2-0)** [Hellyerite at Webmineral.com](http://webmineral.com/data/Hellyerite.shtml)

1. ^ [***a***](#cite_ref-HBM_3-0) [***b***](#cite_ref-HBM_3-1) [Handbook of Mineralogy](http://rruff.geo.arizona.edu/doclib/hom/hellyerite.pdf)

1. ^ [***a***](#cite_ref-Mindat_4-0) [***b***](#cite_ref-Mindat_4-1) [Mindat.org](http://www.mindat.org/min-1853.html)

1. **[^](#cite_ref-5)** Bette, Sebastian; Rincke, Christine; Dinnebier, Robert E.; Voigt, Wolfgang (2016). "Crystal Structure and Hydrate Water Content of Synthetic Hellyerite, NiCO3·5.5H2O". *Zeitschrift für Anorganische und Allgemeine Chemie*. **642** (9–10): 652–659. [doi](/source/Doi_(identifier)):[10.1002/zaac.201600044](https://doi.org/10.1002%2Fzaac.201600044).

1. **[^](#cite_ref-6)** Williams KL,Threadgold IM,Hounslow AW. Hellyerite: A new nickel carbonate from Heazlewoord, Tasmania. *The American Mineralogist*,1959;44:533–538. [\[1\]](http://www.minsocam.org/ammin/AM44/AM44_533.pdf)

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