Greenfields Mine (Caledonia Gold Mine; Three Mile Hill), Coolgardie, Coolgardie Shire, Western Australia, Australiai

Regional Level Types
Greenfields Mine (Caledonia Gold Mine; Three Mile Hill)	Mine
Coolgardie	City
Coolgardie Shire	Shire
Western Australia	State
Australia	Country

Small historic gold mine named after its distance from Coolgardie. North-east of the town just east of the Kalgoorlie-Coolgardie Road. More known now as the site of a gold processing plant operating since 1990, for a number of mines in the Coolgardie area. Caledonia gold mine directly north of the plant.

The former Three Mile Hill gold mine, is located between the mine and the main highway, although this is more noted to describe the processing plant. The historic Jim Cairns shack is located immediately south of the plant.

Gold production in the area began around 1897, with the principal lease called Caledonia. The mining was shallow down to 10 metres of open cuts and stopes on quartz veins and stockworks within mineralised metagabbro units. A London company operated the lease at the time, with well known mining identity Zebina Lane involved.

Bulk sampling occurred in 1947 from a small open cut by New Consolidated Goldfields (Australia) Pty Ltd. The following year D and E.P Clews owns the lease, who farm it out under option to Adelaide based Victory Exploration. New Consolidated Goldfields re-acquired the lease in 1965, and explored it until 1968.

Local prospectors conducted near surface mining in the late 1970's without a great deal of success. In 1985, Goldfan began purchasing and consolidating several leases in the area. In 1990. an open pit, 850 metres long by 280 metres wide by 170 metres deep was excavated, and the Three Mile Hill processing plant constructed next to it. The Great Eastern Highway had to be re-aligned to allow the mine to go ahead.

The mine and plant closed in 1999. The plant resumed in 2002, after the discovery of the high grade Empress deposit south of Coolgardie. Since this time, the consolidation of leases has continued to a point one company owns most of the leases surrounding Coolgardie which it generally calls the Coolgardie Project.

In 2003, Herald sold half its interests at Coolgardie to MPI/Pittston for 3.475 million Australian dollars. The remaining half was sold in February 2005 to the Redemption Joint Venture of Austminex and Matador. Shortly after Austimex changed its name to Focus Minerals, while Matador merged with Committee Bay Resources.

Focus took over the entire project in May 2008 for 36.6 million Australian dollars. The company has explored and mined several deposits in the Coolgardie area. Perseverence was the first in 2008. It toyed with the idea of bulldozing the town to get to the gold underneath, but common sense prevailed.

The mine is part of a 500 metre thick differentiated tholeiitic gabbro sill, which extends for 20 kilometres striking east-west to the north of Coolgardie. The central part of the sill is quartz rich with significant gold. The north-east side of the pit shows a sharp contact between the mineralised and un-mineralised parts of the gabbro. The north-west side of the pit shows the contact between the gabbro, and overlying basalt unit, and a thin (under 10 m) black shale horizon with quartz-feldspar porphyry intrusion. The mineralised unit is within the G2 Gabbro, which is 100 to 150 metres thick of ferrohornblende-plagioclase-ilmenite-quartz with minor garnet. The mineralised unit within this is narrow (under 0.5 m), 50 to 100 metres long, brittle, bucky quartz-calcite-amphibole-arsenopyrite-pyrrhotite veins, and associated alteration haloes. Arsenopyrite is the dominant sulphide, with associated gold.

The mine has produced 2 513 000 tonnes of ore for 2.12 g/t yielding 5328 kg gold to June 1994.

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