Otwayite

Otwayite, Ni2CO3(OH)2, is a hydrated nickel carbonate mineral. Otwayite is green, with a hardness of 4, a specific gravity of 3.4, and crystallises in the orthorhombic system.

Otwayite
General
CategoryCarbonate mineral
Formula
(repeating unit)		Ni2CO3(OH)2
Strunz classification5.DA.15
Crystal systemOrthorhombic
Unknown space group
Unit cella = 10.18, b = 27.4, c = 3.22 [Å]; Z = 8
Identification
ColorBright green
Crystal habitSprays of Fibrous bundles oriented perpendicular to veinlet walls; spherules and claylike coatings
Mohs scale hardness4
LusterSilky to waxy
DiaphaneityOpaque to translucent
Specific gravity3.41
Optical propertiesBiaxial
Refractive indexnα = 1.650 nγ = 1.720
Birefringenceδ = 0.070
PleochroismWeak
DispersionVery strong
References[1][2]

Occurrence

Otwayite is found in association with nullaginite and hellyerite in the Otway nickel deposit. It is found in association with theoprastite, hellyerite, gaspeite and a suite of other nickel carbonate minerals in the Lord Brassey Mine, Tasmania. Otwayite is found in association with gaspeite, hellyerite and kambaldaite in the Widgie Townsite nickel gossan, Widgiemooltha, Western Australia. It is also reported from the Pafuri nickel deposit, South Africa. It was first described in 1977 from the Otway Nickel Deposit, Nullagine, Pilbara Craton, Western Australia and named for Australian prospector Charles Albert Otway (born 1922).[2]

References
  1. Mindat.org
  2. Handbook of Mineralogy
  • Nickel, E. H.; Robinson, B. W.; Davis, C. E. S.; MacDonald, R. D. (1977). "Otwayite, a new nickel mineral from Western Australia" (PDF). American Mineralogist. 62: 999–1002.
  • Nickel, E. H.; Hallbert, J. A.; Halligan, R. (1979). "Unusual nickel mineralization at Nullagine, Western Australia". Journal of the Geological Society of Australia. 26 (1–2): 61–71. Bibcode:1979AuJES..26...61N. doi:10.1080/00167617908729067.
  • Henry, D. A. & Birch, W. D. (1992): Otwayite and theophrastite from the Lord Brassey Mine, Tasmania. Mineral. Mag. 56, 252-255.
  • Andersen, P., Bottrill, R. & Davidson, P. (2002): Famous mineral localities: The Lord Brassey mine, Tasmania. Mineral. Rec. 33, 321-332.
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