Denver — The Cresson gold mine, part of the Cripple Creek & Victor joint venture, southwest of Colorado’s Pikes Peak, is producing ore at greater than its design capacity.
Originally designed to crush 7.5 million tons per year, the open-pit/heap-leach mine is operating at the annual rate of 11 million tons.
South Africa’s
Together with the new crushing facility, the operation will more than double the size of the leach pad in an effort to boost gold production to 400,000 oz. per year by 2003. In all, the joint venture expects to spend US$150 million on the expansion.
AngloGold acquired the property in January 1999 when it picked up the gold assets of Luxembourg’s Minorco. The remaining stake is held by Pacific Stock Exchange- listed
Once in possession, AngloGold immediately began looking at possibilities for expansion. Under the current plan, it will replace the overworked system with a new, US$45-million crushing circuit. A new FFE Minerals gyratory crusher will serve as the primary crusher, feeding four conventional Norberg cone crushers running in parallel. The system will reduce the size of the ore to 0.5 in diameter, less than the current 1.5 inches.
By the end of 2001, the operation expects to have ordered six Euclid 290-ton haul trucks to replace the 17 smaller, 85-ton trucks. Two more are planned for 2002, says James Komadina, president of AngloGold North America.
The trucks will mine 60 million tons of ore and waste per year, at a stripping ratio of 2-to-1. Ore from the new crushing plant will then be trucked to the leach pad.
Here too, the company has some changes planned. When the mine opened, in 1993, the leach pad held only 50 million tons. The company has since expanded the pad several times to the current capacity of 105 million tons.
Under the current expansion plan, laid out in an October 2000 feasibility study, the valley-fill leach pad will grow to a capacity of 260 million tons, making it the largest valley-fill pad in the world. (Eventually, though, the pad at the Veladero gold project in Argentina, owned by
Highway project
However, to expand the Cresson pad to 260 million tons, the company has some shuffling to do. The mine sits snugly between the towns of Cripple Creek and Victor, which, historically have produced a total of 22 million oz. gold since the early 1900s. Unfortunately, the two towns are connected by state highway 67, which bisects the mining operation, particularly the leach pad. The company has received permission from the state to relocate the highway to allow for the pad expansion. The plan calls for a 1.8-mile section of the highway to be moved and for a 1,200-ft. bridge to be built over the creek, at the base of the pad.
Work on the highway project began in September of last year; paving of the road should begin this August and be completed by October.
Other infrastructure changes include building additional facilities to increase the rate at which cyanide solution is applied to the pad.
While power has been a hot issue in the western U.S., particularly regarding copper mines in Arizona and gold mines in Nevada, Cripple Creek sees no such difficulties, says Komadina. Currently, the joint venture is paying US4 per kilowatt-hour. However, it expects soon to sign a power contract with Midwestern supplier West Plains Energy for less. West Plains operates a coal-fired plant 20 miles to the south. The mine is its largest consumer.
The leach-pad expansion is expected to cost US$45 million; other infrastructure costs account for the remainder of the US$150-million price tag.
The expansion plan incorporates mineralization found in the mine’s four main ore deposits: Cresson Main, East Cresson, North Cresson and South Cresson. Overall reserves stand at in 172.8 million tons averaging 0.03 oz. per ton, equivalent to 5.2 million oz. gold.
Main and East
The Main and East deposits are currently being mined. Mining is to begin at the North deposit in 2002, and at the South deposit in 2007.
Mineralization at Cripple Creek is hosted in a Tertiary diatreme complex intruded into Precambrian granites. Gold occurs by itself or is associated with oxides after pyrite.
The operation contains an additional 4.8 million oz. in resources (208 million tons of 0.023 oz. per ton), which, with infill drilling, could be converted into reserves.
AngloGold has spent US$4-6 million per year on infill drilling in the past three years in preparation for the expansion. It budgeted another US$4.5 million for resource conversion in 2001. The infill program, which is nearly half done, will likely total 400,000 ft. Historically, the company has been able to convert 60% of its resources into reserves, says Komadina.
The company has no exploration outside of the mine area, though it is spending US$250,000 on deep drilling for possible underground targets beneath each of the four main deposits.
AngloGold expects the expansion project will kick in by the second half of 2002, churning out a total of 350,000 oz. for that year. In 2003, production should hit 400,000 oz. annually at life-of-mine cash operating costs of US$170 per oz.
The operation is expected to contribute 260,000 oz. gold in 2001 at a cash operating cost of US$189 per oz., and at a total cost of US$230 per oz.
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