|Latitude & Longitude (WGS84):||21° 52' 56'' South , 120° 6' 12'' East|
|Latitude & Longitude (decimal):||-21.88236,120.10334|
|Köppen climate type:||BWh : Hot deserts climate|
Grant's Hill refers to a gold mine, geographic hill, and historically an area of this goldfield, near the mine and hill. This is common for areas immediately surrounding Nullagine for gold mines. Named after early Nullagine gold pioneer, Alex Grant, who had an initial alluvial lease here from 1887.
Grant's Hill is about one kilometre north north-west of the Nullagine town site, and is near the southern extent of what was many old mines, now largely cleared bulldozed areas, which extend a further one kilometre north and east to the Nullagine Weir.
The site is unusual as gold is found in a conglomerate formation. This has unfairly been described as similar to the Rand deposits in South Africa. With apologies to experts on South African gold locations, the differences are as follows. Government geologist on the issue, K.J. Finucane states the only similarity is gold is found in both locations in conglomerate and associated with pyrite. At Nullagine, the ore bodies occur as distinct flat horizons in a relatively homogenous mass of conglomerate, with no marker beds. At Johannesburg, gold is found in relatively thin lenticular bodies of conglomerate, which forms small portions of sediments, consisting also of shale, quartzites and grit. The Nullagine goldfield would not be nearly as rich as the Rand deposits, described as low grade, and largely active only from 1895 to about 1906.
The conglomerate is rounded and sub-angular fragments with abundant pyrite and oxide material. The fragments consist of quartz, ironstone and shale, cemented in iron stained kaolin, with numerous cavities, at one time filled with pyrite crystals, now pseudomorphed to limonite. Unoxidised pyrite crystals, pyrite grains and pebbles form fragments up to one eighth of an inch in diameter. Within the conglomerate is found generally low grades of gold, and minor diamonds.
Modern exploration company, Nova Resources, suggest the Golden Crown gold location, one kilometre north-east of Grant's Hill, forms the apex of a channel fan deposit, created by a meandering ancient river, which deposited sediments into the Nullagine embayment. Grant's Hill deposits and those to the north formed when the sea level rose, and waves cut access to the lower reaches of the fan, leaving behind boulder lags, and associated heavy minerals like gold and pyrite.
At Grant's Hill there are six stacked reefs (horizons?), 0.5 to 2 metres thick, and less than a total of 20 metres from the surface.
Grant's Hill historically was the largest gold deposit on this goldfield, and the richest gold in gravels at the base of the hill. Known originally as the Trinity lease. GML 681, formerly Trinity No. 1 GML 422. 12 acres. Adjacent to the Grant's Hill South lease.
After Alex Grant pegged his lease, the next information is 1891, stating a lease had been pegged at Grant's Hill, by prospectors McNamarra and McKenzie (surnames). It states the gully at the foot of the hill for 200 yards long had produced over 3000 ounces of alluvial gold, although the figure is likely to have been much more.
The mine was developed by the North West Australian Goldfields Limited from around 1896 to 1898, who also owned the Trinity, Freak of Nature, Freak of Nature Extended, Exchange and Success leases, totalling 62 acres. Development work was being retarded by a lack of machinery, but crushings are recorded for the period.
A.E. Morgan was involved in developing several gold mines across Western Australia, and at one point was Premier of the State. He formed the British Exploration of Australian Ltd in London, and took over several mines in the Nullagine area. Its stated at the time in 1901, the Grant's Hill lease contained three separate conglomerate veins averaging over 3 feet wide, at 15 dwt to the tonne. The conglomerate ran flat through the hill. The company was in liquidation by 1910. Gibb-Maitland states the lease in 1908, was home base for the Nullagine Conglomerate Gold Mines Ltd.
In 1916, it is reported the Nullagine Mining Company controlled the lease, along with at least nine nearby. In 1936, the Paringa Mining and Exploration Limited from the Golden Mile Kalgoorlie, held an option over the lease from owners J. Thomson and C.H. Counsel, the latter having first inspected the lease in 1889. It also controlled several other nearby mines, amounting to leases covering 160 acres. To this point Grant's Hill had produced 3433 tonnes of ore for 1780.24 ounces of gold.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
5 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
2500 - 2800 Ma
|Archean sedimentary and volcanic rocks|
Age: Neoarchean (2500 - 2800 Ma)
Stratigraphic Name: Fortescue Group
Comments: Pilbara Craton
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
2500 - 4000 Ma
|Mosquito Creek Formation|
Age: Archean (2500 - 4000 Ma)
Stratigraphic Name: Mosquito Creek Formation
Comments: sedimentary siliciclastic; argillaceous detrital sediment; synthesis of multiple published descriptions
Lithology: Sedimentary siliciclastic; argillaceous detrital sediment
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia).