Processing
Ore from the Rosebery mine is processed in the concentrator where the valuable minerals containing zinc, lead, copper, gold and silver are separated from waste rock. The concentrator uses a number of processes to recover the valuable minerals to form mineral concentrates suitable for sale to smelters and refineries where the pure metals are produced.
Processing begins by crushing ore as it is trucked from the underground workings. The ore passes through three crushers to reduce it to 8mm particles. The ore particle size is further reduced in tumbling mills where water is added and steel balls grind the ore to less than one tenth of a millimetre. At this size the fine grains of valuable mineral are freed from the waste rock.
Gold is the first mineral to be recovered. Fine gold particles are recovered from the ore slurry in a high “G” gravity separator. This gold and some associated silver are melted into bars sold as doré to gold refiners.
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Ore is tipped into the crusher.
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Tumbling mill.
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Flotation circuit.
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Copper, lead and zinc are recovered next. These metals occur in the ore as sulphide minerals which can be efficiently recovered by a process called froth flotation. Chemicals or reagents are used to make these minerals water repellent so that they attach to air bubbles introduced into the slurry of finely ground ore particles and water. A specific reagent is used for each sulphide mineral so each one is recovered separately. Some of the gold is associated with the copper minerals and most of the silver is associated with the lead minerals so those metals form a part of the copper and lead concentrates. The remaining waste material, referred to as tailings, is pumped to a tailings storage facility.
The Rosebery concentrator has operated continuously for 75 years, a remarkable achievement in Australia’s mining history.