Glencore reported on June 25 that the new, 1-km-deep hoisting shaft at its Ernest Henry mine near Cloncurry in northwest Queens-land, Australia, had begun operations. The shaft is a key element of an A$589 million project to transition the Ernest Henry mine from open-pit to underground production. Mine production will ramp up from 3 million to 6 million mt/y in 2015, and production of metal in concentrate will similarly double to 50,000 metric tons per year (mt/y) of copper and 70,000 oz/y of gold over an extended mine life to 2026.

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The headframe at Glencore’s Ernest Henry mine duringinstallation of the ‘skyshaft.’

The Ernest Henry underground project began in December 2009 and has included more than 50 km of underground development accessed by a 6-km decline; construction of associated infrastructure, including an underground primary crusher and 1.2 km of below-surface and overland conveyors to transport ore to and from the hoisting system; installation of a 75-m-high permanent headframe to house the hoisting system, which has capacity to lift around 1,000 mt/h; and reconfiguring the concentrator to align with the underground production rate.

The underground mine utilizes an innovative sublevel caving mining method and is currently operating across four production levels. Ore has been trucked to surface via the decline since December 2011, and the decline will continue to be used as the main access point for the underground workforce over the life of the mine.

Glencore COO for copper assets in North Queensland Mike Westerman said, "Our assets in Mount Isa and at Ernest Henry accounted for around 14% of Glencore's global copper production in 2013. This investment in Ernest Henry has effectively added 14 years to the life of the mine to 2026."

As of December 2013, Ernest Henry had total underground ore reserves of 74 million mt, grading 1.04% copper and 0.53 g/mt gold.

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