Near surface alluvial gold was discovered in 1862 by James Lamb, and soon around two thousand miners had arrived. The Hunter brothers sank two shafts with a connecting drive 1885 to 1887, discovering an auriferous lead 1.2 to 1.5 metres thick, being the basal part of gravels. The Golden Lion Sluicing Company began in 1896, and shortly after the Nokomai Hydraulic Sluicing Company which lasted into the 1920's. The Nokomai Gold Mining Company operated with a huge dragline through the 1930's, ceasing in 1943. The only quartz reef discovered was in Commissioners Gully. L & M Mining dredged an area of the valley for gold in a joint venture with the Nokomai Station owners from 1991, with the bottom 2 metres of the gravels being profitable.

The basement rock is greenish-grey psammitic semi-schist and schist of the Caples Terrane, with sub-ordinate interlayered black pelitic schists, and rare metachert horizons.

The gravels largely consist of the same material, from under 10 metres thick at Donkey Flat at the upper end, to up to 35 metres thick in the lower valley. The gravels consist of fluvial and intercalated fan gravels, weakly auriferous, with a high auriferous boulder lag gravel base.

Discontinuous gravel terraces are also found on the north-west side of the lower valley, 120 metres above the valley floor. The gravel is the same as the bedrock, except rare scarlet coloured jasperitic chert cobbles in the terrace gravels, and mine tailings here. The terrace gravel is cemented by brown clay.

A 3 metre thick yellowish clay section within the valley floor gravels can be traced discontinuously for 3 kilometres in the lower valley. Layers of dark brown peat with a high clay content is found sporadically within the gravels.

Gold is an Au-Ag-Hg alloy in the upper part of the valley, while at the lower end is an Au-Ag alloy. Both types look the same, and can only be distinguished by chemical analysis.

A Pleistocene aged abandoned river channel is incised into the schist on the north-west margin of the plain. This is clay cemented greywacke semi-schist and schist, with intercalated transverse boulder gravel in a clay matrix.
Gold in the abandoned channel is an Au-Ag alloy. Distinct populations of almandine, spessartine, and grossular garnets are found in the channel, with magnetite up to 4 mms. The base of the channel was extensively worked for gold.

Cinnabar as small veins in bedrock, and detrital up to 1 cm can be found in the upper part of the valley around Shark Bay Creek, and Victoria Gully. A stream entering from the south-east in the lower valley contains Hg 20-37%, with gold coated in Au-Ag-Hg alloy, and drops of liquid mercury in the gravels.

The area is part of the Nokomai pastoral station, although access maybe possible if staying at the station in accommodation provided to tourists.

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References