Crushing and MillingCrushing and milling of gold bearing rock is done so that free gold particles can be liberated and collected; and gold dissolving fluids can act on as much surface area as possible to dissolve the maximum amount of gold. How much crushing is needed will depend on the properties of the ore rock (hardness, porosity, brittleness); the nature of the gold within the ore (coarse, fine, stuck to sulphides) and the processing method employed (heap leach, gravity, flotation, CIL/CIP).
Crushing Crushing refers to breaking rock down to a size fraction something like gravel or a little finer. This size is typically needed for heap leach operations. Rock will typically pass through several stages of crushing, with incrementally finer output at each stage. The final crushed product will then either be taken by conveyor belt or truck to the heap leach pad, or first be agglomerated. Milling Milling refers to breaking rock down to a size fraction so fine it is like a powder. This size is typically needed for Gravity, Flotation and CIL/CIP operations. Crushing and milling works somewhat like chewing one's food, it allows digestion to work better than if you swallowed things whole. This is because the more surface area equals more ability for processing to act on an ore and so extract more gold. |
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