versão On-line ISSN 2411-9717
J. S. Afr. Inst. Min. Metall. vol.114 no.5 Johannesburg Mai. 2014
The South African mining industry has been mainly associated with gold, which is understandable given that it was the gold mines of the late nineteenth century that were really the beginning of the industry as we know it. Currently platinum mining is making headlines regarding long strikes, and coal mining and Eskom are also much in the news. Diamonds have always featured in the media, to an extent that varies with time. However, base metals have never received any prominence, although they have formed part of the industry's contribution for many decades. Copper, nickel, lead, and zinc are produced in South Africa. Palabora Mining Company produces copper, Nkomati Nickel produces nickel, and Black Mountain produces copper, zinc, and lead. In addition, copper, nickel, and cobalt are by-products from the base metals refineries associated with the four major platinum producers.
Copper is produced in the form of cathodes from electrorefining and electrowinning. Nickel is produced in the form of metal cathodes by electrowinning, or as metal briquettes or nickel sulphate. Cobalt is produced in the form of metal briquettes or cobalt sulphate. There is no primary production of lead metal, and there is no longer any primary production of zinc metal since the closure of Zincor at the end of 2011. With the exception of lead and zinc, the beneficiation of base metal ores in South Africa is thus well developed.
The beneficiation of base metal ores will always provide a significant challenge to extractive metallurgists - I speak from personal experience with many base metal projects in southern Africa. The flow sheet options are considerable, and in many instances mineral processing, pyrometallurgy, and hydrometallurgy need to be applied.
If we broaden our view of base metals to the southern African region, then we see a copper and cobalt industry of global significance. The Central African Copperbelt that spans Zambia and the Democratic Republic of Congo (DRC) is a world-class mineral province. Although mined tonnage does not compare with the copper porphyries of North and South America, the higher copper grades mean that actual copper production is not that far behind. Zambia and the DRC are 5th in global copper production when their output is combined. Beneficiation of copper ores, both sulphide and oxide, in Zambia and the DRC is well developed, with most of the copper being produced as cathode metal via electrorefining or electrowinning. There is a significant diversity of copper concentrators, smelters, and refineries within Zambia and the DRC. When the Nchanga tailings leach complex in Zambia was originally built close to 40 years ago it boasted the world's largest copper solvent extraction and electrowinning plant. At Ndola in Zambia is one of the world's few refineries processing copper refinery anode slimes, producing selenium, tellurium, silver, and gold as by-products.
The Copperbelt constitutes the world's largest deposit of cobalt, which is associated with the copper in oxide and sulphide minerals. There are a number of cobalt plants which beneficiate oxide and sulphide cobalt concentrates into cathode metal via electrowinning. Zambia and the DRC produce about half the world's cobalt.
There are nickel mines in Botswana and Zimbabwe, and zinc, lead, and copper mines in Namibia. Zinc and lead are also produced on a small scale in Zambia and the DRC. This all highlights the extent of base metals production in southern Africa and illustrates why the SAIMM organizes a base metals conference every two years. The next conference will be held in Zambia in 2015, with a copper / cobalt theme. The event will be convened in conjunction with our Zambia and DRC branches, and will serve as a vehicle for promoting them, as well as provide a means to motivate the hosting of the International Copper Conference in Southern Africa.