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
Otwayite from the type locality in Otway Nickel deposit
General
Category	Carbonate mineral
Formula (repeating unit)	Ni2CO3(OH)2
IMA symbol	Otw^[1]
Strunz classification	5.DA.15
Crystal system	Orthorhombic Unknown space group
Unit cell	a = 10.18, b = 27.4, c = 3.22 [Å]; Z = 8
Identification
Color	Bright green
Crystal habit	Sprays of Fibrous bundles oriented perpendicular to veinlet walls; spherules and claylike coatings
Mohs scale hardness	4
Luster	Silky to waxy
Diaphaneity	Opaque to translucent
Specific gravity	3.41
Optical properties	Biaxial
Refractive index	nα = 1.650 nγ = 1.720
Birefringence	δ = 0.070
Pleochroism	Weak
Dispersion	Very strong
References	^[2]^[3]

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).^[3]

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. Mindat.org
3. 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.