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
- 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.
- Mindat.org
- 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.