# Violarite

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Supergene sulfide mineral

Violarite General Category Sulfide mineral Thiospinel group Spinel structural group Formula (Fe2+Ni23+S4) IMA symbol Vio[1] Strunz classification 2.DA.05 Crystal system Isometric Crystal class Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) Space group Fd3m Unit cell a = 9.46 Å; Z = 8 Identification References [2][3][4]

**Violarite** ([Fe](/source/Iron)2+[Ni](/source/Nickel)23+[S](/source/Sulfur)4) is a [supergene](/source/Supergene_(geology)) sulfide mineral associated with the [weathering](/source/Weathering) and [oxidation](/source/Oxidation) of primary [pentlandite](/source/Pentlandite) [nickel](/source/Nickel) sulfide [ore](/source/Ore) minerals.

Violarite crystallises in the [isometric](/source/Cubic_(crystal_system)) system, with a hardness of 4.5 to 5.5 and a specific gravity of about 4, is dark violet grey to copper-red, often with verdigris and patina from associated copper and arsenic sulfides, and is typically in amorphous to massive infill of lower [saprolite](/source/Saprolite) [ultramafic](/source/Ultramafic) [lithologies](/source/Lithology).

Violarite has a characteristic violet colour, hence the name from the [Latin](/source/Latin) 'violaris' alluding to its colour especially when viewed in polished section under a microscope.

## Paragenesis

Violarite is formed by oxidisation of primary sulfide assemblages in nickel sulfide mineralisation. The process of formation involves oxidation of Ni2+ and Fe2+ which is contained within the primary [pentlandite](/source/Pentlandite)-[pyrrhotite](/source/Pyrrhotite)-[pyrite](/source/Pyrite) assemblage.

Violarite is produced at the expense of both pentlandite and pyrrhotite, via the following basic reaction;

Pentlandite + Pyrrhotite --> Violarite + Acid

- (Fe,Ni)9S8 + Fe(1-x)S + [O](/source/Oxygen)2 → Fe2+Ni23+S4 + H2SO3

Violarite is also reported to be produced in low-temperature metamorphism of primary sulfides, though this is an unusual paragenetic indicator for the mineral.

Continued oxidation of violarite leads to replacement by [goethite](/source/Goethite) and formation of a [gossaniferous](/source/Gossan) boxwork, with nickel tending to remain as impurities within the goethite or haematite, or rarely as carbonate minerals.

## Occurrence

Violarite is reported widely from the oxidised [regolith](/source/Regolith) above primary nickel sulfide ore systems worldwide. It is of particular note from the Mount Keith [dunite](/source/Dunite) body, Western Australia, where it forms an important ore mineral.

It is also reported from open cast mines around the Kambalda Dome, and Widgiemooltha Dome, in association with [polydymite](/source/Polydymite), [gaspeite](/source/Gaspeite), [widgiemoolthalite](/source/Widgiemoolthalite) and [hellyerite](/source/Hellyerite), among other supergene nickel minerals.

### Economic importance

Violarite is an important transitional ore in many nickel sulfide mines, as it has increased nickel tenor (Ni% as a total of sulfide) and occupies a position within the mineralised profile where it must be extracted to pay for development down to the most valuable fresh mineralisation.

Violarite mineralisation requires different [metallurgy](/source/Metallurgy) to primary nickel sulfides, due to the different nature of its gangue and its flotation properties. This may require additional treatment and processing, so in some cases low-grade violarite mineralisation is considered refractory ore.

## 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-2)** [Mindat.org](http://www.mindat.org/min-4187.html)

1. **[^](#cite_ref-3)** [Webmineral.com](http://www.webmineral.com/data/Violarite.shtml)

1. **[^](#cite_ref-4)** ["Handbook of Mineralogy"](https://web.archive.org/web/20120605133136/http://www.handbookofmineralogy.com/pdfs/violarite.pdf) (PDF). Archived from [the original](http://www.handbookofmineralogy.com/pdfs/violarite.pdf) (PDF) on 2012-06-05. Retrieved 2011-05-12.

- Dunn, J.G.; Howes, V.L. (1996). "The oxidation of violarite". *Thermochimica Acta*. 282–283: 305–316. [Bibcode](/source/Bibcode_(identifier)):[1996TcAc..282..305D](https://ui.adsabs.harvard.edu/abs/1996TcAc..282..305D). [doi](/source/Doi_(identifier)):[10.1016/0040-6031(96)02806-7](https://doi.org/10.1016%2F0040-6031%2896%2902806-7).

- Grguric, B.A. (2002), Hypogene violarite of exsolution origin from Mount Keith, Western Australia: field evidence for a stable pentlandite-violarite tie line: Mineralogical Magazine: 66: 313–326.

- Tenailleau, C., Pring A., Tschmann B., Brugger J., Grguric B., and Putnis A. (2006), Transformation of pentlandite to violarite under mild hydrothermal conditions: American Mineralogist: 91: 706–709.

- Thorber, M. R. (1972) Pyrrhotite-the matrix of nickel sulphide mineralization. Newcastle Conference, Australasian Institute of Mining and Metallurgy, May–June, 1972, 51–58.

- Thorber, M. R. (1975a) Supergene alteration of sulphides, I. A chemical model based on massive nickel sulphide deposits at Kambalda, Western Australia. Chemical Geology, 15, 1–14.

- Thorber, M. R. (1975b) Supergene alteration of sulphides, II. A chemical study of the Kambalda nickel deposits. Chemical Geology, 151 117–144.

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