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Going underground
The switch from open pit mining to underground is not simply a technical challenge, Hugh Leggatt discovers. It's all about the impact on people, as well.

On 25 April, 2002, the last production blast took place in the open pit mine at Palabora, one of the world's great copper producers. It was the "steepest and the deepest" section of the pit, reported managing director David Sadler. "The guys have done a great job working right up to the last minute achieving their targets – without injuries."

It is 39 years since the first production blast rocked the slope of a low saddleback hill, the eroded remnant of an extinct volcano in South Africa's eastern lowveld. Sitting over a mineral rich pipe 800m in diameter reaching 1,800m below the surface, the subsequent mine unburdened a horn of plenty – 4.8 million tonnes of copper from 900 million tonnes of ore. But the hard truth is that nothing lasts forever. Knowing this, Palabora miners were ready for the final blast in 2002.

It was not the first time that closure had loomed over Palabora. When the mine was started in 1963 by Rio Tinto, it had an anticipated life of 26 years, to 1989.

Over the years, technological advances, increasing economies of scale and more detailed exploration have added 13 years of production since 1989. In the mid 1980s studies began to assess the feasibility of going underground to mine that part of the mineralized volcanic pipe too deep to reach by open pit from the surface. While this was feasible, it would only be economic if significant improvements in processing could also be made.



Going underground The switch from open pit mining to underground is not simply a technical challenge, Hugh Leggatt discovers. It's all about the impact on people, as well. On 25 April, 2002, the last production blast took place in the open pit mine at Palabora, one of the world's great copper producers. It was the "steepest and the deepest" section of the pit, reported managing director David Sadler. "The guys have done a great job working right up to the last minute achieving their targets – without injuries." It is 39 years since the first production blast rocked the slope of a low saddleback hill, the eroded remnant of an extinct volcano in South Africa's eastern lowveld. Sitting over a mineral rich pipe 800m in diameter reaching 1,800m below the surface, the subsequent mine unburdened a horn of plenty – 4.8 million tonnes of copper from 900 million tonnes of ore. But the hard truth is that nothing lasts forever. Knowing this, Palabora miners were ready for the final blast in 2002. It was not the first time that closure had loomed over Palabora. When the mine was started in 1963 by Rio Tinto, it had an anticipated life of 26 years, to 1989. Over the years, technological advances, increasing economies of scale and more detailed exploration have added 13 years of production since 1989. In the mid 1980s studies began to assess the feasibility of going underground to mine that part of the mineralized volcanic pipe too deep to reach by open pit from the surface. While this was feasible, it would only be economic if significant improvements in processing could also be made.
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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