Osborne

The Osborne underground copper-gold mine is located in the state of Queensland in northeastern Australia. It is 195 kilometers southeast of the inland town of Mount Isa and 720 kilometers west-southwest of the coastal city of Townsville.

Stoping methods vary depending on the ore profile and plunge within the deposit, with uphole benching producing the majority of production tonnes. Paste fill has been introduced to reduce hanging wall instability and allow greater recovery of the resource.

Mining operations commenced at the Inheritance satellite deposit at Trekelano in May 2006. Ore is mined by conventional open pit methods and transported to the Osborne mill.

The treatment plant includes a gyratory crusher, a secondary cone crusher, a rod mill/ball mill grinding circuit, Knelson gravity gold concentrator circuit and a copper flotation circuit. About 10% of total gold production is from the gravity circuit in the form of doré. Copper-gold concentrate is trucked to the Phosphate Hill railhead and transported to the Xstrata port storage and ship loading facility in Townsville.

In 2007, production at Osborne totaled approximately 42,000 ounces of gold and 86 million pounds of copper. Total cash costs were $304 per ounce of gold and $1.37 per pound of copper¹. The proven and probable mineral reserves at December 31, 2007 are estimated at 82,000 ounces of gold and 173 million pounds of copper².