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Copper grinding process

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This is the process of separating precious minerals from waste rock. At Britannia the copper ore contained just over 1% copper (though in the early years it was around 8%). The remaining 99% was mostly waste rock, called ‘tailings’. In the rock, chemical and physical bonds hold the valuable minerals to the waste rock. Some ore contains minerals in an elemental or almost pure form such as native copper, native silver, etc., but most valuable minerals are compounds, in this case Chalcopyrite (CuFeS2).

The process used to separate the minerals is called ‘concentrating’. Breaking the chemical bonds and separating the elemental copper form the other mineral components is called ‘smelting’ and ‘refining’. This was done elsewhere as there was never a smelter located at Britannia Beach. In the Mill No. 3, the various stages in the milling process took up all of the building. A number of different types of equipment were used to mill the ore as it flowed down from level to level. Some of this equipment is explained below.

Ball mill for copper grinding processing

Grinding – Ball Mills

The ore would then flow into ball mills similar to the rod mills. Steel balls inside the ball mills were about the size and weight of a shot-put ball. These grinding mills rotated anywhere form 1 to 5 times per second.

The end product of the milling process is ore ground to the consistency of sugar or salt (small enough to pass through mesh having 100 holes per square inch). This material is called ‘fines’ and is still mixed with water as it leaves the milling circuit.