Trevorite

Trevorite
Pale green nepouite appears to be far richer on this specimen, than the black with a green or brown tint trevorite. It is hard to distinguish the two.
General
Category	Oxide minerals Spinel group Spinel structural group
Formula	NiFe3+2O4
IMA symbol	Trv [1]
Strunz classification	4.BB.05
Dana classification	7.2.2.5
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Fd3m (no. 227)
Unit cell	a = 8.41 Å; Z = 8
Identification
Color	Black, greenish hue
Crystal habit	Granular to massive, rare as minute octahedra
Cleavage	None
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	5
Luster	Metallic to sub-metallic
Streak	Brown
Diaphaneity	Opaque, transparent in thinnest fragments
Specific gravity	5.164
Refractive index	n = 2.41 (calculated)
Other characteristics	Highly magnetic
References	[2] [3] [4]

Trevorite is a rare nickel iron oxide mineral belonging to the spinel group. It has the chemical formula NiFe³⁺₂O₄. It is a black mineral with the typical spinel properties of crystallising in the cubic system, black streaked, infusible and insoluble in most acids.

There is at least partial solid solution between trevorite and magnetite, with many magnetites from ultramafic rocks containing at least trace amounts of Ni. Fe²⁺ and Mg²⁺ may substitute for Ni in trevorite.

Discovery and occurrence

It was first described for an occurrence in the Bon Accord Nickel Deposit, Bon Accord, Barberton, Mpumalanga, South Africa, in 1921 and was named for Major Tudor Gryffydd Trevor (1865–1954), who was a mining inspector in South Africa. ^{[4] [2]}

In the Bon Accord deposit it occurred as a contact deposit between an ultramafic intrusion and a quartzite. In an occurrence at Mount Clifford, Australia, it occurs associated with a nickel sulfide orebody adjacent to a gabbro which intruded peridotite. Associated minerals include nimite, willemseite, nickeloan talc, violarite, millerite, reevesite and goethite at Bon Accord; and with native nickel, heazlewoodite and millerite at Mt. Clifford. ^[2]

It has also been reported from the Logatchev-1 hydrothermal field on the Mid-Atlantic Ridge; in the Hatrurim Formation in the Negev Desert in Israel; the Josephine Creek District, Josephine County, Oregon and the Gabbs District of Nye County, Nevada. ^[4]

References

1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
2. Handbook of Mineralogy
3. Trevorite on webmineral.com
4. Trevorite on Mindat.org

• Deer, W. A.; R. A. Howie; J. Zussman (1992). An Introduction to the Rock-forming Minerals. Harlow, Essex: Longman. pp. 559–563. ISBN   978-0-470-21809-9.