Copper

Copper is found in nearly every home and vehicle, in parts and appliances, and in instruments used in all aspects of modern living, infrastructure and technology. In many respects, modern life would not have been possible without copper.

There is a good reason why copper has played an important role in human civilization for thousands of years. It can be easily shaped, moulded, rolled into sheets, or drawn into thin wire. It blends readily with other metals to form useful alloys such as brass and bronze. It does not easily rust, and it's an excellent conductor of electricity and heat.

How copper is mined
Copper is mined either at via open pit mines or underground mines.

In open pit copper mining, the ore is broken free and reduced to a manageable size by blasting. Huge shovels are used to load the broken ore into haul trucks, which take it to the crusher.

Underground mining of copper usually involves block caving, a technique that uses gravity to extract copper ore from the mine. In block caving, mining engineers create a cave below the ore deposit, causing the ore to break away from the ceiling and fall into the cave. Loaders then transport the ore to an underground crusher, and shafts convey the ore from the crusher for processing.

In the crusher, the ore is broken into smaller pieces of less than 25 centimetres in diameter. Crushed ore is then loaded on to a conveyor belt which takes it to the concentrator. In the concentrator, semi-autogenous and ball mills grind the ore until it is a fine powder.

Ground ore is then mixed with water, chemicals and air in flotation cells, which causes the copper-bearing minerals to stick to air bubbles in the cells. The bubbles float to the surface of the mixture and are collected as liquid concentrate which contains about 27 per cent copper.

Smelting and refining copper
The concentrate is then pumped to a smelter where it is dried in a large rotating dryer before it is sent into a flash smelting furnace. In the furnace, the concentrate is broken down into three products: gases (containing sulphur), slag (solid waste material containing silica and iron) and copper matte, which is 70 per cent copper.

Once cooled, the copper matte is ground and fed into a flash converting furnace to remove most of the remaining impurities, resulting in a molten copper, called blister, which is about 98 per cent copper.  Further refining occurs in furnaces before the copper is cast into large, thick plates called anodes. Each anode weighs in the vicinity of 315 kilograms and contains about 99.6 per cent copper.

At the refinery, racks of anodes are submerged into an acid solution which is interleaved with stainless steel cathodes. Over 10 days, an electric current is sent between the anodes and cathodes, causing copper ions to migrate from the anode to the cathode. Impurities such as gold and silver fall off the anode into the solution. This process produces a plate on the cathode that is 99.99 per cent pure copper.

An anode will usually produce two cathodes, each weighing about 127 kilograms. These are stripped from the stainless steel sheets and strapped together into 2300 kilogram bundles for transport.

More information on copper mining, refining and smelting at Kennecott Copper Utah can be found at the Kennecott Copper Utah website.

Other products extracted with copper
Copper mining and extraction also results in the extraction of gold, silver and molybdenum. Molybdenum, in particular, has become a major earner for the Rio Tinto Copper group, with Kennecott Utah Copper's mine now the fourth largest molybdenum producer in the world.

For more information on our other products, see our corporate fact sheets.