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Why are gold ores crushed before cyanide leaching?

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A worker in safety gear walks beside a conveyor belt carrying ore at the Tanami gold mine in the arid, expansive landscape of the Tanami Desert. — gold processing The Tanami gold mine, Northern Territory, Australia.

Gold ores are crushed as part of a process called comminution to physically liberate valuable minerals from their interlocked state within hard, tough rock masses.12

Because gold is often disseminated within these rock structures, crushing and subsequent grinding are essential to expose the gold particles. This size reduction is critical for cyanidation because the cyanide leach solution must have direct access to the gold to dissolve it. If the gold remains trapped or surrounded by waste rock or interfering minerals, the cyanide cannot reach the metal to initiate the dissolution process. By reducing the ore to a suitable size, processors ensure that the solvent can effectively percolate through or mix with the material, maximizing the recovery of the gold.1342