Ohai Mine, Ohai, Southland District, Southland Region, New Zealandi
| Regional Level Types | |
|---|---|
| Ohai Mine | Mine |
| Ohai | - not defined - |
| Southland District | District |
| Southland Region | Region |
| New Zealand | Country |
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Latitude & Longitude (WGS84):
45° 55' 42'' South , 167° 56' 29'' East
Latitude & Longitude (decimal):
Locality type:
KΓΆppen climate type:
Coal.
The Ohai Coalfield is 80 kilometres north-west of Invercargill.
It is contained within a north-east limb of a major syncline, within a fault controlled east-west basin. The Ohai Group rocks consists of three units, being the Wairio Coal Measures, New Brighton Conglomerate, and Morley Coal Measures.
The Wairio Coal Measures are the oldest, and up to 51 metres thick. It consists of conglomerate, coarse sandstone, shale, and under 1.3 metre thick high ash coal seams. The New Brighton Conglomerate is conglomerate with lesser bands of sandstone, mudstone, shale, and coal.
The economically important Morley Coal Measures are the youngest of the three, but characterised by splitting, wash-outs, and are lenticular in nature. Clays, boulder conglomerate, carbonaceous mudstone, siltstone, sandstone and coal seams are found in the measures. Some of the feldspars have altered to kaolinite, and to a lesser extent montmorillonite. The coal measure is divided into six recognisable coal seams from youngest being No. 3 seam, Couper seam, Morley No. 2 seam, Linton Main seam/Morley No. 1.5 seam, Morley No. 1 seam, and the Star seam. These reach a maximum 30 metres thick, but are highly variable. The coal is sub-bituminous to bituminous.
The overburden is Quarternary gravels, interbedded with mudstone, siltstone and rare muddy sandstone.
(Brothers, 1959) studied heavy mineral concentrates in the coal measures. These were found to contain colourless or pink garnets, rare blue-green hornblende, tourmaline of varying colours, sideroplesite golden brown to lemon yellow surrounding an opaque core , yellowish to golden sphene often enclosing ilmentite, and in addition andalusite, apatite, biotite, chlorite, epidote, iron ore, kyanite, rutile, sidero dolomite, topaz, zircon, zoisite, calcite, feldspar, muscovite, quartz, and siderite. All are grain size, and are probably little evident in hand specimens.
There was an Ohai Coal Syndicate operational from when the coalfield was opened in 1917. It bordered to the west of the Wairaki 4 Mine, just north of Morley Stream. At the end of World War Two, the New Zealand government controlled State Coal purchased most of the mines in the Ohai area. This later morphed into Solid Energy.
Solid Energy closed the Wairaki Mine in 2003, and this was replaced by the Ohai open cut mine, named after the bordering town. The mine closed in 2009, when it lost the contract with its largest customer, a dairy processing factory at Clandeboye. In 2011, Solid Energy announced it had found a further 50,000 tonnes of coal, and the following year had produced 35,000 tonnes of coal for local domestic use. The mine had employed 300 workers in the 1980's.
Shortly after the mine closed again, when Solid Energy was liquidated after unwise investments into coal briquetting, and turning coal into diesel fuel experiments. The mine was subsequently sold to Palmer MH groups Greenbriar, and as of 2018, limited mining continues for local domestic use.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsMineral List
2 valid minerals.
Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
| β 'Feldspar Group' Reference: Sherwood, A.M., Lindqvist, J.K., Newman, J., Sykes, R. (1992) Depositional controls on Cretaceous coals and coal measures in New Zealand (in Controls on the Distribution and Quality of Cretaceous Coals, Ed. McCable, P.J., Parrish, J.T.), The Geological Society of America, Special Paper 267, 339-344. |
| β Kaolinite Formula: Al2(Si2O5)(OH)4 Reference: Sherwood, A.M., Lindqvist, J.K., Newman, J., Sykes, R. (1992) Depositional controls on Cretaceous coals and coal measures in New Zealand (in Controls on the Distribution and Quality of Cretaceous Coals, Ed. McCable, P.J., Parrish, J.T.), The Geological Society of America, Special Paper 267, 339-344. |
| β Montmorillonite Formula: (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O Reference: Sherwood, A.M., Lindqvist, J.K., Newman, J., Sykes, R. (1992) Depositional controls on Cretaceous coals and coal measures in New Zealand (in Controls on the Distribution and Quality of Cretaceous Coals, Ed. McCable, P.J., Parrish, J.T.), The Geological Society of America, Special Paper 267, 339-344. |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 9 - Silicates | |||
|---|---|---|---|
| β | Kaolinite | 9.ED.05 | Al2(Si2O5)(OH)4 |
| β | Montmorillonite | 9.EC.40 | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 Β· nH2O |
| Unclassified Minerals, Rocks, etc. | |||
| β | 'Feldspar Group' | - | |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | β Kaolinite | Al2(Si2O5)(OH)4 |
| H | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| O | Oxygen | |
| O | β Kaolinite | Al2(Si2O5)(OH)4 |
| O | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| Na | Sodium | |
| Na | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| Mg | Magnesium | |
| Mg | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| Al | Aluminium | |
| Al | β Kaolinite | Al2(Si2O5)(OH)4 |
| Al | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| Si | Silicon | |
| Si | β Kaolinite | Al2(Si2O5)(OH)4 |
| Si | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| Ca | Calcium | |
| Ca | β Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
References
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Year (asc) Year (desc) Author (A-Z) Author (Z-A)Lake Wakatip Mail newspaper (1945) Purchase of Collieries in Southland, issue 4676, 01 February 1945.
Brothers, R.N. (1959) Heavy minerals from Southland. Part 2: Upper Cretaceous Lower Tertiary coal measures, New Zealand Journal of Geology and Geophysics, 2:4, 788-798.
Warnes, M.D. (1988) The Palynology of the Ohai Coalfield, Southland. (unpublished thesis, MSc), University of Canterbury.
Sherwood, A.M., Lindqvist, J.K., Newman, J., Sykes, R. (1992) Depositional controls on Cretaceous coals and coal measures in New Zealand (in Controls on the Distribution and Quality of Cretaceous Coals, Ed. McCable, P.J., Parrish, J.T.). The Geological Society of America, Special Paper 267, 339-344.
Craw, D., Mulliner, T., Haffert, L., Paulsen, H-K, Peake, B., Pope, J. (2008) Stratigraphic controls on water quality at coal mines in Southern New Zealand. New Zealand Journal of Geology and Geophysics, 51:1, 59-72.
The Southland Times newspaper (2011) Ohai Coal on Sale Again, 07 September 2011.
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