Kalgoorlie is a famous mining town lying in the semi-arid outback region 800km inland from Perth. Kalgoorlie serves as a supply base for the many gold, nickel and base metal mines in the region, as well as a rural and government administration centre. While Kalgoorlie has grown into a fully-fledged town, it is doubtful most of the population would remain without the large investment by the mining industry into the region.
There is a huge gold mine in the town itself, along the Kalgoorlie-Boulder Golden Mile. This is the Superpit; the largest open cut gold mine in the world. The Kalgoorlie region is famous among gold fossickers as a productive area for finding gold nuggets with metal detectors. Millions of dollars in gold nuggets have been found with detectors here during the past 30 years, however, it is the major mines, which have brought wealth to Western Australia and many residents of Perth’s affluent suburbs, such as Peppermint Grove, Nedlands and Cottlesloe.
A lot of effort has gone into mapping and understanding the geology of the region since it is the geology that controls the location and type of mineral deposits that occur. The Kalgoorlie region lies in an Archean craton. Cratons are the oldest remnants of crust left on earth and a feature of these cratons is the existence of belts of rocks called greenstones separated by granitic and gneissic rocks.
Some of the more interesting rocktypes around Kalgoorlie occur in the greenstone belts. The characteristic red and white jaspilite and associated banded iron formation (BIF) form ridges upto several hundred metres long. Elsewhere, near Cue and in the Hamersley Ranges, individual bands can be traced for tens of kilometres. Chert, jasper, hematite and magnetite can be collected from the jaspilite and BIF’s. Schistose rocks containing micas tremolite, actinolite, serpentine, talc, pyroxenes and/or olivine are widespread within the greenstone belts. Various other rocktypes, including meta-basalts, pyroxenite, dunites, andesites, dolerites, gabbros and rhyolites are also widespread. If you are lucky enough to be invited into one of the minesites, there is the opportunity to collect samples of various sulphide minerals, such as pyrrhotite, pentlandite, pyrite, arsenopyrite and chalcopyrite.
Most fossickers go to the Kalgoorlie region to prospect for gold with metal detectors. Mostly, they camp out in the bush around old diggings. Many of the old diggings and locations have storybook names originating from the 1800’s. Locations such as Bailey’s Reward, Hannan’s Find and Larkinville are named after the original miners. Others, such as Murrin Murrin, Widdgemooltha and Mulgarrie have Aboriginal origins.
Most gems that occur around Kalgoorlie are of the semi-precious or ornamental type, such as jasper, chert, chalcedony and hematite.