Latitude & Longitude (WGS84):	27° 38' 29'' South , 117° 52' 45'' East
Latitude & Longitude (decimal):	-27.64162,117.87929
GeoHash:	G#: qe5fdrvpf
Locality type:	Mine
Köppen climate type:	BWh : Hot deserts climate

Adjoins to the south of the Island Eureka Mine on 'The Island' portion of the goldfield. The Chicago and Shamrock were initially separate leases, but later were worked together.

Chicago is the original discovery of gold on the field by the Webb brothers. After picking up all the surface nuggets they could find they left. They told the find later on meeting Regan and Kegney (surnames), who hurried to the spot. After chipping some gold from the outcrop they too abandoned the area. It was then taken over by Dave Beany, who dug a 10 x 12 foot pothole, but with little in the way of tools, food and water he too left.

The 6 acre Chicago lease was developed by Rutter, Cause, Young and Murphy (surnames), who struck gold within two weeks of taking over the lease. They sunk a shaft near the boundary to 28 feet deep to a gold shoot, then drove 70 feet to a second shoot. At this level they dollied 2000 oz of gold. A second shaft was sunk to 25 feet on a reef 4 feet 6 inches wide, and a short distance away a third shaft was sunk to 33 feet. There were plans to connect all the shafts, with those on the Shamrock lease. The reef was said to be saddle shaped near the surface, with two outcrops. One source describes Rutter as an alcoholic, whiskey his poison of choice. This is somewhat unfair, considering publicans on these historic goldfields often came away with more money than the miners. Rutter later died on a gold expedition elsewhere in Western Australia.

The adjoining Shamrock was 5 acres, in an elevated position, and owned initially by Cause, Began and Pierce (possibly Caws or Regan) (surnames) as a reward claim. They initially dug a 10 x 8 foot cutting into the outcrop, and it is said found enormous quantities of gold. Specimens were sent to Geraldton for a public showing in 1892. The reef was 18 inches on the surface but widened to 3 feet 6 inches 30 feet down, the reef in parts said to be solid gold, with 1000 oz taken. The reef was Fe oxide stained honeycombed quartz.

The leases accessed a quartz reef along the western side of a large quartzite bar, both dipping gently west. The quartzite bar formed the footwall of the reef, and it was at this contact the best gold was found. Rich gold patches were found along this contact by the early prospectors.

In May 1895, the Chicago and Shamrock leases were under offer to Hugh Walker, but it is unclear if he was acting alone, or representing a syndicate. Reports continued to come to light over the years of rich patches being discovered. August 1895 specimens showing more gold than quartz went on display at a local bank. October 1897, one patch dollied 1000 oz. April 1898, the directors of the syndicates controlling the Chicago, Shamrock and Chicago North leases, decided to amalgamate, under one entity called Chicago United. In one 5 tonne crushing in 1899 they produced 123 oz of gold.

Mid 1902 the Island Eureka South Gold Mining Company NL was formed in Adelaide to work the leases, with 4000 pounds in capital raised. Walter Arnold was appointed mine manager. Various equipment was installed. Initially, the crushings were successful, and this led the company to install a five head battery and engine in 1904. The first crushing at the battery of 100 tonnes only produced 18 oz. Retired mine manager and major shareholder, A.C. Russell, was despatched from Adelaide by the company to investigate. He produced a positive report, but shareholders were unwilling to invest more money. January 1904, the company was wound up.

One of the original pioneers of the goldfield, Tom Hughes, returned in 1915 to work the Chicago/Shamrock as a prospecting lease. In later years, especially the 1930's, the leases were combined into larger holdings, mentioned in other Mindat mine listings for this goldfield.

Officially the Chicago leases produced 75.10 tonnes at 402.45 oz, Shamrock 58 tonnes at 391.10 oz and during the Island Eureka South years 31 tonnes for 25.55 oz. It is thought the figures are incomplete.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

2 valid minerals.

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

Neoarchean - Mesoarchean 2500 - 3200 Ma ID: 3188304

Archean volcanic rocks Age: Archean (2500 - 3200 Ma) Comments: Yilgarn Craton Lithology: Greenstone belt; mafic-ultramafic volcanic rocks 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]

Archean 2500 - 4000 Ma ID: 805661

volcanic and sedimentary rocks 74483 Age: Archean (2500 - 4000 Ma) Description: Rhyodacitic porphyry, volcaniclastic rocks, tuff, para-amphibolite, quartzite, mafic schist, amphibolite, felsic volcanic rocks, mafic volcanic rocks, banded iron formation, siliciclastic rocks, ultramafic rocks, chert Comments: sedimentary; igneous volcanic; synthesis of multiple published descriptions Lithology: Sedimentary; igneous volcanic 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). [5]

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

References