The main ore mineral of copper in Australia (and worldwide) is chalcopyrite (CuFeS2). Bornite (Cu5FeS4), covellite (CuS) and chalcocite (Cu2S) are important sources in the world, and many ore bodies also contain some malachite (CuCO3.Cu(OH)2), azurite (Cu3(CO3)2.Cu(OH)2), cuprite (Cu2O), tenorite (CuO) and native copper. The sulphides, which yield most of the copper produced throughout the world, generally occupy the deeper parts of lodes which have not been exposed to weathering. Near the surface they are altered by oxidation and other chemical actions to the native metal, oxides and carbonates. These secondary copper minerals may form rich ore in the upper parts of many deposits, and, owing to their characteristic green or blue colour, even small amounts are easily seen in the rocks in which they occur.
Australian Resources and Deposits
Copper is widely distributed in Australia in rocks of Precambrian and Palaeozoic age (more than 250 million years old).
Australia's resources of copper are largely at the Olympic Dam copper-uranium-gold deposit in South Australia and the Mount Isa copper-lead-zinc deposit in Queensland. Other important copper resources are at the Northparkes copper-gold, CSA copper-lead-zinc and Girilambone copper deposits in New South Wales, the Ernest Henry, Osborne and Mammoth copper deposits and copper-gold deposits at Selwyn in Queensland and copper-zinc deposits at Golden Grove and the Nifty copper deposit in Western Australia.
Australia's main copper mining centres are in the Mount Isa/Cloncurry region of Queensland and at Olympic Dam in South Australia. The Mount Isa mine, which also produces large tonnages of lead, zinc, and silver, is currently the largest copper producer in Australia, and is one of the world's biggest underground mines. At Mount Isa, the copper ore bodies are separate from the lead-zinc-silver ore bodies, thus enabling independent production of the two ore types. Across Australia, relatively small amounts of copper are also recovered as a by-product of silver-lead-zinc, nickel and gold mining.
Several important copper deposits have been discovered in the last thirty years. By far the largest of these is the copper-uranium-gold deposit discovered in 1975 at Olympic Dam in South Australia where expanded annual production will soon surpass that at Mt Isa. Other important discoveries include the Northparkes copper-gold deposit (NSW) in 1977, Cadia copper-gold deposit (NSW) in 1993, Benambra copper-zinc deposit (Vic) in 1978, Scuddles (Golden Grove) copper-lead-zinc deposit (WA) in 1979, Selwyn gold-copper deposit (Qld) in 1980, Nifty copper deposit (WA) in 1983, Eloise copper-gold deposit (Qld) in 1988, Osborne copper-gold deposit (Qld) in 1990, Ernest Henry copper-gold deposit (Qld) in 1991, Tritton copper deposit (NSW) in 1995, and Ridgeway copper-gold deposit (NSW) in 1996.
Australia in the World
Australia has about 6 per cent of the world's economic copper resources and is ranked third after Chile (25 per cent) and the USA (16 per cent). In production Australia is ranked fifth after Chile, USA, Indonesia and Canada.
Mining and Processing
Although large copper deposits are mined by open-cut methods in many of the major producing countries, most of the copper ore produced in Australia comes from underground mines.
At some Australian mines, the copper is leached from the ore to produce a copper-rich solution which is later treated to recover the copper metal. At the Mount Gordon mine (formerly Mammoth) at Gunpowder in Queensland the ore is first broken and set out on leach pads where it is dissolved by a sulphuric acid solution to leach out the copper. The copper-rich solution is then pumped to the solvent extraction plant to separate the copper as a copper complex. This is concentrated and the solution is passed to the electrowinning plant to recover the copper. The copper cathodes produced by electrowinning contain 99.99 per cent copper which is suitable for electrical uses. This entire process, known as solution exchange electrowinning (SX-EW), is also used at other mines treating copper oxide ores, most notably at Girilambone and at Nifty.
The traditional method used at most mines involves the ore being broken and brought to the surface for crushing. The ore is then ground finely before the copper-bearing sulphide minerals are concentrated by the flotation process, which separates the grains of ore mineral from the waste material, or gangue. Depending on the type of copper bearing minerals in the ore and the treatment processes used, the concentrate can contain between 25 and 57 per cent Cu. The concentrate is then processed in a smelter.
Smelters are operated at Mount Isa and Olympic Dam. Copper refineries are operated at Townsville, Olympic Dam and Port Pirie (a small refinery subsidiary to the large lead-zinc refinery). Various methods of smelting are used to convert the concentrates to copper metal. One method is to melt them with fluxes in a smelter furnace to produce copper matte, which is a mixture mainly of iron and copper sulphides usually containing 50 to 70 per cent Cu. The molten matte is poured into a converter, which contains more fluxes, and converted into blister copper, which is about 98 to 99 per cent pure. The blister copper is tapped, further refined in an anode furnace and finally electrolytically refined to pure cathode copper.
At Olympic Dam the concentrate is flash-smelted directly to blister copper. In this process copper concentrate is fed into the smelter with oxygen-enriched air. The fine concentrate reacts or 'flashes' instantaneously as the sulphur fraction of the copper sulphides is burnt and becomes sulphur dioxide gas. Molten copper and slag fall to the hearth of the smelter. The slag forms a layer on the surface of the molten blister copper. The blister copper is removed periodically for further purifying in an anode furnace and electrolytically refined.
Copper is alloyed with other metals to give it special properties. Bronze is an alloy of tin and copper. The earliest bronzes were natural alloys derived from mineral deposits which also contained tin. Brass is an alloy of zinc and copper and is used extensively in marine applications because of its resistance to corrosion.
Uses
Copper is an excellent conductor of electricity. More than half of the copper consumed is used in electrical generators and motors, electrical power and lighting fixtures, electrical wiring, radio and television sets, computers and almost everything electrical. Copper also conducts heat well and is used for thin-walled copper tubing in air conditioning and refrigeration units, motor vehicle radiators, home heating systems, steam condensers etc. Copper's corrosion resistance and ease with which it can be joined make it suitable for plumbing fittings and water reticulation systems, automotive fuel lines, sea water desalination plants and hydraulic systems. The blue-green colour of treated timber is the result of copper naphthanate and copper-chrome-arsenate which have been introduced under pressure to help protect the wood from borers. Copper sulphate is used as a fungicide and as a trace element in fertilisers. Copper is also used for making coins and scientific instruments and in decorative applications.
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