Cannington

The Cannington underground mine located 800 kilometres south west of Townsville is 83 kilometres from the nearest township of McKinlay. It has its own airstrip and village accommodation is located three kilometres from the mine site. A shuttle bus takes workers to and from the airstrip, the mine and the village.

Cannington Mine Area Subjected to Flooding During the wet Season

The area is prone to flooding although the average rainfall is only 250 mm. Most of this rain falls between the months of November and March leaving the area semi-arid for most of the time. Rivers in the area are dry most months of the year.

Cannington Mine is the World's Largest Silver Mine

The Cannington Mine is the world's largest producer of silver and lead that is produced from the one operation. This amount of silver equals six percent of the world's silver and seven percent of the world lead production. The lead concentrate that leaves the Cannington Mine contains 70 percent lead and more than 3,000 grams a tonne of low impurity silver. Zinc concentrate contains 250 grams of silver and 50 percent zinc.

Access to the Cannington Mine is via a Decline

The Cannington underground mine is accessed by means of a decline ramp from the surface although there is a hoisting shaft that can handle 1.8 million tonnes of ore annually. In 2008 the mine processed 3.1 million tonnes of ore which produced, in concentrate form, 163,000 wet metric tonnes of zinc, more than 31 million ounces of silver and 404,000 wet metric tonnes of lead.

Long Hole Stoping Mining Methods Used at the Cannington Mine

Mining underground at the Cannington Mine is undertaken via the long hole open stoping method when extracting ore from the main thicker hanging wall orebodies. Ore broken away from the stopes is loaded from draw points at the bottom of each individual stope and taken to the surface by haulage skips after being hauled along the level and tipped into one of many ore passes.

Cannington Mine Decline Extends Underground for 5,250 Metres

The Cannington decline is 5.5 metres wide by 5.2 metres high with a gradient of one in eight to the 450 metre level, from thereon it has a gradient of one in seven. The decline has a total length of 5,250 metres. Its main function is to provide mobile equipment and personnel access as well as acting as an intake of fresh air.

Hoisting Shaft at the Cannington Mine Begins at the 650 Metre Level

The hoisting shaft has a diameter of 5.6 metres and is constructed to a depth of 650 metres. It has a tower mounted friction winder and two nine tonne skips that are counter balanced on rope guides. The skips are hoisted from the loading station on the 610 metre level and can hoist ore to the surface at a speed of 12 metres a second. Once on the surface the skip is tipped by means of a tipping scroll built into the head-frame that empties the ore into a waiting surface bin that transfers the ore to the processing facilities stockpile area.

Because of regular flooding during the wet season all surface infrastructure, shafts and the decline are raised above ground level to above predicted flood levels. Once a stope has all the ore extracted from it, a paste backfill is put in place to fill the void to stabilise the area and make it safe for the creation of adjoining stopes. Paste backfill is made up of 80 percent solids that are mixed with tailings from the processing plant along with about five percent cement. This is fed underground by gravity feed through boreholes that pipe the backfill directly into the open stope.The Cannington Mine, that is wholly owned by South32, consists of the underground mine and a metallurgical processing plant. It also consists of a rail loading infrastructure at Yurbi, 15 kilometres from Cloncurry and a state of the art mineral concentrate handling facility at the Townsville port.