Xstrata Transitions to Underground Mining at Ernest Henry

In this photo taken about a year ago, the collar and headframe structure foundations have been completed
on a new shaft at Xstrata Copper’s Ernest Henry mine. The shaft, which will be used to hoist ore from a
depth of 1,000 m, is scheduled for commissioning in 2013. (Photo courtesy of Xstrata Copper)
Xstrata Copper started underground mine production at its Ernest Henry operation 38 km northeast of Cloncurry in north Queensland in early December 2011, marking the site’s transition from open-pit mining, which is now complete, to under-ground mining and magnetite processing. The underground production start is a major milestone in an A$589-million pro-ject to extend Ernest Henry operations to at least 2024.

During the first phase of underground mining, ore is being trucked via a decline at a rate of approximately 3 million mt/y for processing at an on-site concentrator into concentrate containing about 25,000 mt/y of copper and 35,000 oz/y of gold. Second phase development is based on sinking of a hoisting shaft to a depth of 1,000 m. Following commissioning of the shaft in 2013, production will ramp up to 6 million mt/y of ore and 50,000 mt/y of copper and 70,000 oz/y of gold in concentrate.

Ernest Henry concentrate is trucked 157 km to Xstrata Copper’s Mount Isa smelter for smelting to anode. Anode is then railed to Townsville for refining to cathode at the company’s copper refinery.

The Ernest Henry orebody is an iron oxide-copper-gold deposit, with magnetite being the form of iron ore. Magnetite is lib-erated during the copper-gold concentrat-ing process and was previously discarded as tailings. The Ernest Henry extension project included construction of a 1.2-mil-lion-mt/y magnetite concentrate plant, which was completed in February 2011. The new plant allows the magnetite to be recovered from the concentrator tailings stream and sold as an important by-prod-uct, reducing the amount of tailings sent to the on-site storage facility.

The first regular train-load of magnetite concentrate departed Cloncurry for Towns-ville April 30, 2011, and Xstrata Copper became Queensland’s first magnetite con-centrate exporter June 15, when the first shipment of magnetite concentrate depart-ed the Port of Townsville for Asia.

As featured in Womp 2012 Vol 01 - www.womp-int.com