Rio Tinto | Minerals and Metals for the world

Bingham Canyon in Utah was the first large scale open pit mine. It started in 1904, and is still going strong. The rapid and on going increase in the size of open pit mining equipment since the 1960s, and the associated benefits of economy of scale, has resulted in open pit mining gaining a larger share of the production of most metals and minerals. Among metals, this is particularly true for copper, iron ore, and nickel.

One pointer to the robustness of open pit copper operations is that in 2001 they accounted for nearly 60 per cent of the Western world's copper reserves. Only a few countries, notably Australia and Poland, rely largely or entirely on underground reserves for future copper production.

Factors that have had a strong impact on the industry, both in terms of production and lower costs, are the size and quality (ore grade) of some open pit copper discoveries, and the development of SxEw (solvent extraction and electro-winning) leaching technology, which recovers copper from low grade ores. A glance at the industry cost curve shows the low cost producers are dominated by open pit operations. Two in which Rio Tinto has a significant interest particularly stand out: Escondida in Chile with its high copper grade and Grasberg in Indonesia with its large gold by-product.

The production picture for gold and silver is complicated by the large amounts produced as a by-product of mining other metals. The country that produces most gold (South Africa) does so predominantly from underground mines. Elsewhere many of the largest producers are open pit mines.

Nature conspires with economics to favour open pit mining - but only up to a point. It provides an abundance of outcropping and near surface mineral deposits that are suited to open pit mining. Often, parts have been enriched by weathering and the ore there is easier to treat. There is no need to invest time and money in sinking shafts. It adds up to an invitation to start from the surface and work downwards.



Bingham Canyon in Utah was the first large scale open pit mine. It started in 1904, and is still going strong. The rapid and on going increase in the size of open pit mining equipment since the 1960s, and the associated benefits of economy of scale, has resulted in open pit mining gaining a larger share of the production of most metals and minerals. Among metals, this is particularly true for copper, iron ore, and nickel. One pointer to the robustness of open pit copper operations is that in 2001 they accounted for nearly 60 per cent of the Western world's copper reserves. Only a few countries, notably Australia and Poland, rely largely or entirely on underground reserves for future copper production. Factors that have had a strong impact on the industry, both in terms of production and lower costs, are the size and quality (ore grade) of some open pit copper discoveries, and the development of SxEw (solvent extraction and electro-winning) leaching technology, which recovers copper from low grade ores. A glance at the industry cost curve shows the low cost producers are dominated by open pit operations. Two in which Rio Tinto has a significant interest particularly stand out: Escondida in Chile with its high copper grade and Grasberg in Indonesia with its large gold by-product. The production picture for gold and silver is complicated by the large amounts produced as a by-product of mining other metals. The country that produces most gold (South Africa) does so predominantly from underground mines. Elsewhere many of the largest producers are open pit mines. Nature conspires with economics to favour open pit mining - but only up to a point. It provides an abundance of outcropping and near surface mineral deposits that are suited to open pit mining. Often, parts have been enriched by weathering and the ore there is easier to treat. There is no need to invest time and money in sinking shafts. It adds up to an invitation to start from the surface and work downwards.
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Review is published by Rio Tinto, 6 St James' Square, London SW1Y 4LD, England Telephone +44 (0)20 7930 2399 Editor: Cherry DeGeer