Alluvial gold.

Gold particles found in Miocene coal measures, overlain by Pliocene quartz gravels from ancient river channels. Most of the quartz pebbles of the gravels are the result of decomposition of clay lithic clasts during sedimentary recycling. Quartz gravels at the mine contain abundant Mn rich garnet clasts from the Otago Schist, and up to 10% chromite clasts in heavy mineral sands, possibly from the Dun Mountain Ophiolite Belt.

The sites contain the basal Gore Lignite Measures, with seams up to 10 metres thick, with quartz pebbles and sands between, overlain with the Waimumu Quartz Gravels, containing quartz pebbles and some greywacke.

Quartz clasts contain evidence of a lower greenschist facies foliation, defined by up to 1 mm muscovite, chlorite, epidote and titanite, separated by lamaellae of quartz and albite.

Coarse gold particles are found up to 1 mm in diameter in quartz gravels and sands, within the Gore Lignite Measures, however the overlying Waimumu Quartz Gravels is barren. The gold particles consist of under 0.1 mm detrital gold flakes welded together along the flake margins. The particles are irregular in shape, and show surface protrusions and features, with spongy margins. The edges may enclose quartz and kaolinite. Examples of up to sixty detrital grains have been found welded together. The gold flakes may have marcasite overgrowths. Occasionally gold is found in quartz.

Gold appears to have only been discovered in the 1890's when local farmers sank wells. James Humphries had operated butchers shops locally, and decided in 1893 to purchase a farm, discovering gold when sinking a well. A couple of dredging companies operated in the first decade of the 20th Century on his property, and the Waimumu Sluicing Company in the 1930's. Nomad Mining began extracting gold from a shallow pit next to the stream around 2010, but then became more interested in silica, mining quartz aggregate from a pit a short distance away.

The field next to the pit, holds an agricultural field day every second February, attracting 30 000 people.

Other Regions, Features and Areas containing this locality

References