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US gold operation’s life-of-mine extended
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6th December 2002
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Over a century since mining first began in the historic Criple Creek mining district, 80 km from Colorado Springs in the US state of Colorado, the Cripple Creek & Victor mine (CC&V) continues to produce gold.

In fact, following the latest AngloGold expansion of this massive openpit operation, the ore processed at the mine will almost double, from 9,8- million t/y to 18,1-million t/y, while gold output will rise by nearly half to 362 000 oz/y.

The $194-million project will extend the life of the mine by four years to 2013, enabling the production of 2,8-million incremental ounces at a cost of $176/oz.

Underground mining at CC&V was undertaken for 70 years until 1961.

Then all mining activity lapsed for a decade until the start-up of small-scale surface mining using heap-leaching methods.

In 1991 surface mining was started on a large scale and continued to grow with the start of production from CC&V’s Cresson mine in early 1995.

The mine was acquired by AngloGold from Minorco in 1998, with the mining giant owning 67% of the mine and managing the operation, and Golden Cycle Corporation owning the balance.

“As a result of new bulk-mining technology we have been able to convert what was a historic mined-out high-grade underground mining district into a low-grade opencast mine (reserve grade 1,02 g/t),” explains AngloGold head corporate technical group Benjamin Guenther.

“We are mining through the old underground stopes, some of which can be quite wide, and are using ground-penetrating radar to see where the openings are, so as not to damage equipment and cause safety hazards,” he explains.

The ore at CC&V is treated using a valley-type heap-leach process, with gold being recovered by activated carbon.

As part of the expansion project, the existing crusher was decommissioned and a new crushing system was introduced.

Increased efficiency of the crusher system was needed in order to double production.

Secondary crushers, able to take material down to quarter inch size, were also installed.

The absorption-desorption recovery plant responsible for processing the pregnant solution from the leach was doubled in size.

This system was commissioned in the third quarter of this year.

The project also saw the replacement of the existing fleet of trucks, which were primarily Caterpillar F777, with ten Euclid trucks that are hauling 285 tons per truck at CC&V.

These new trucks have ac electric drive wheel motors, which results in faster speeds both up and down ramps, increasing efficiency.

Unlike blasts underground in South Africa, which typically produce about 100 t of material, a single blast at this operation produce tens of thousands of tons of material, meaning the larger trucks greatly increase productivity.

“Like all of our projects, we are constantly looking for new opportunities, and the possibility of expansion beyond 2013 has not been ruled out.

“Further expansion will depend upon the economics at the time, including the gold price, capital cost and operating expenditure,” indicates Guenther.

One of the factors limiting further expansion is how much bigger the heap-leach can get.

By 2013 it will already be large, with nearly 200-million tons of ore on the single heap.

The waste dumps are being rehabilitated concurrently to mining operations. However, the heap-leach does not lend itself to reclamation during operation, and rehabilitation of this heap will be possible only after closure.
Edited by: marisa rodrigues

 

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