Harbour Lights Gold Mine (Leonora Central), Leonora, Leonora Shire, Western Australia, Australiai

Regional Level Types
Harbour Lights Gold Mine (Leonora Central)	Mine
Leonora	Town
Leonora Shire	Shire
Western Australia	State
Australia	Country

The Harbour Lights Gold Mine is 1.5 kilometres north-west of Leonora, between the Goldfields Highway and airport. It is now marked by a large, abandoned, water filled open pit.

Historically it was seen as a large low grade proposition, its size and lack of refractory ore in the upper levels attracting attention. Its low grade, and that two thirds of the gold remained in the sands with high treatment costs at the state battery to process the sands, leading often to a loss of interest.

The first reports were found from 1904, although it could have been a prospector show before this. From this date to 1920, saw a revolving door of syndicates, companies and prospectors take over the mine, with some mining, and some more progressing no further than the intention to mine. Most of the syndicates were local, and some from Leonora. Foley, Beckinsale, Olsen and Gleeson (surnames), worked the mine for the longest period in the years before World War One.

From 1920 to the beginning of World War Two, activity at the mine was spasmodic. The mines department conducted a drilling campaign in 1928. Peter Hill and C. Finch took over the mine in 1932. In 1934 they sold it to the Leonora Central Gold Mine Company Ltd, who worked it with a small plant for one year in 1935. During this short period the mine was known as Leonora Central, before reverting again to Harbour Lights.

Exploration began again at the mine in the late 1970's to early 1980's, with four exploration companies finding very little. Aurora Gold (W.A.) Pty Ltd and Carr Boyd Minerals Pty Ltd, discovered an economic deposit, and open pit mining commenced in 1985, ceasing in 1994 when the ore body had been depleted. Plants were constructed to treat both the oxide ore, and sulphide ore under 40 metres from the surface. Sons of Gwalia purchased the mine in 1995.

The first BIOX plant in Australia, opened in 1992, was operational at Harbour Lights. This is where bacteria oxidation is used to extract the gold.

The Harbour Lights deposit is in the northern section of the Sons of Gwalia Shear Zone, which dips locally moderately east. Rocks within the shear zone are mainly chlorite schist and talc-chlorite schist, with several lenses of undeformed basalt, gabbro and amphibolite. Carbonate alteration is common, and there are numerous dykes and porphyries. It is overlain by sheared komatiites, then a succession of high magnesium tholeiitic basalts, with thin persistent slate.

At Harbour Lights there are boudins from microscopic to 30 metres in length, consisting of quartz, carbonate and felsic alteration assemblages, commonly micaceous, forming tabular bodies.

The deposit is atypical for local gold mines, in that the mineralisation predates the last deformation, and has developed in a normal rather than reverse motion shear zone.

Gold mineralisation is related to D1 quartz veins, formed at very high fluid pressures, parallel to well developed north-east to east dipping D1 cleavage, both deformed in steep dipping and extensional D2 shears. Gold mineralisation lies in a zone of quartz-dolomite-biotite-chlorite-fuchsite schist, and talc-carbonate-biotite schist, with several lenticular felsic bodies, and thin quartzite layers. The fuchsitic selvages adjacent to quartz-carbonate are the most intensely mineralised with gold. Mineralisation tends to pinch out between boudins.

Another source adds, most gold is hosted in the magnesium tholeiitics, with three zones of mineralisation in highly deformed and altered sequences of mafic and ultramafic rocks 200 metres thick. The bulk of the ore is in the Hanging Wall and Central Zone, with less near the Footwall. Mineralisation it states is complexly distributed in lenticular domains. Magnesium rocks have altered to fuchsite schist, komatiites and biotite schist to chlorite schist, and high magnesium tholeiites to chlorite-quartz-calcite-ankerite schist, with large amounts of ferroan magnesite. Native gold is found as minute inclusions in and around arsenopyrite grains, which replace pyrite.

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