Earnscleugh dredge, Alexandra, Central Otago District, Otago Region, South Island, New Zealand

Latitude & Longitude (WGS84):	45° 14' 46'' South , 169° 21' 27'' East
Latitude & Longitude (decimal):	-45.24611,169.35767
Köppen climate type:	Cfb : Temperate oceanic climate

Massive piles of dredge tailings are found just west of Alexandra. To reach cross the bridge heading south, and almost immediately turn onto Earnscleugh Road, then Marshall Road to the car park. A 30 minute trail leads to a viewing platform, and a longer trail passes old dredge ponds, water races, and dredge remnants like buckets and trommels. It represents around one hundred years of dredging history for the location from the 1860's to 1963.

American Horatio Hartley, and Irishman Christopher Reilly discovered 1100 ounces of gold in Cromwell Gorge in August 1862. This led to a wild gold rush, with miners sluicing the rivers for gold. When the gold available declined, mechanical dredges were employed on the rivers, and neighbouring flats, starting in earnest during the New Zealand dredging boom of the 1890's.

In June 1896, the Earnscleugh No. 1 dredge started on a 95 acres area, which had been granted to Charles Weaver, James Kelman, and engineer Alexander Black. The dredge was designed by E. Roberts, built in part by Black's company, Cossens and Black from Dunedin. The dredge was 27.4 metres long, with 0.76 capacity buckets, and could dredge down to 11.6 metres. H.G. Downie was dredgemaster.

The operation was highly successful in finding gold, and in 1898 the Earnscleugh No. 2 dredge started, with the largest bucket capacity of any dredge in New Zealand at that time. The dredge was 29.8 metres long, with an elevator 21.9 metres long, again in part built by Cossens and Black. It would burn 6 tonnes of coal in a 24 hour period.

The Earnscleugh No. 3 Dredging Company held a neighbouring lease, also with Weaver and Kelman as principal shareholders. The Earnscleugh No. 3 dredge started in 1902. It was 40.2 metres long, with a 36.9 metre long elevator, and could dredge down to 15.2 metres. This company was liquidated, and absorbed by the main Earnscleugh Gold Dredging Company Limited in 1901.

This new reconstruction had Charles Weaver, Patrick Weaver, James Kelman (as the dredge owner), Alexander Black (engineer), John McPherson, Ann Gilchrist, Margaret McPherson, and Elizabeth Reid as shareholders.

The re-named Earnscleugh No. 4 dredge was purchased as partially built from the unsuccessful Fraser Flat Company in 1905, but it was never put into operation.

The Earnscleugh No. 5 dredge was purchased in 1907 from the Dunstan Lead Dredging Company, and converted to electricity powered in 1908.

In 1909 the No. 1 dredge was decommissioned, and the same fate fell the No. 2 dredge in 1916, No. 5 dredge in 1920, and No. 3 dredge in 1923, with the company voluntarily wound up in August 1924. By 1918, the dredges had obtained 56 150 ounces of gold, in what was a long lived and highly successful operation.

The Clutha Dredging Company was registered in London in April 1934, and started with a huge dredge called Alexandra, at 50 metres long, 13.4 metres wide, and could dredge to a depth of 19.8 metres. It first worked the river from Alexandra to Coal Creek, however in 1943 it was working the eastern flats of the Clutha River, and in 1949 moved to the Earnscleugh Flats. This operation ceased in 1963, due to rising costs, the fixed price of gold at the time, and a lack of available land.

In 2009, L & M Mining began a pilot gold dredging operation, just west of the old tailings, which was ramped up to full scale production in 2010. In 2013, the dredge sank, and was re-floated, however the operation closed in 2014, blamed on low gold prices, and the high value of the New Zealand dollar. The mine was then listed for sale.

Mineral List

1 valid mineral.

Regional Geology

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

Holocene 0 - 0.0117 Ma ID: 1351106	OIS1 (Holocene) mining waste Age: Anthropocene (0 - 0.0117 Ma) Description: Well sorted sandy quartz, schist and sandstone gravels in dredge tailings and sluicing deposits; anthromorphic fossils. Comments: Holocene human-made deposits. Age based on known Lithology: Major:: {gravel},Minor:: {sand} Reference: Heron, D.W. . Geology Map of New Zealand 1:250 000. GNS Science Geological Map 1. [13]
Quaternary 0 - 2.588 Ma ID: 1313962	Late Quaternary glacial outwash deposits Age: Pleistocene (0 - 2.588 Ma) Stratigraphic Name: Pakihi Supergroup Description: Muddy to sandy gravel. Comments: Zealandia Megasequence Terrestrial and Shallow Marine Sedimentary Rocks (Neogene) Lithology: Gravel Reference: Edbrooke, S.W., Heron, D.W., Forsyth, P.J., Jongens, R. (compilers). Geology Map of New Zealand 1:1 000 000. GNS Science Geological Map 2. [12]
Triassic - Permian 201.3 - 298.9 Ma ID: 3189657	Paleozoic-Mesozoic crystalline metamorphic rocks Age: Phanerozoic (201.3 - 298.9 Ma) Stratigraphic Name: Haast Schist Comments: Caples Terrane Lithology: Metawacke; greenschist/almandine amphibolite grade metasedimentary/metavolcanic schist 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. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

External Links