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How can sulfide minerals prevent cyanide solution from reaching gold particles?
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gold processing
The Tanami gold mine, Northern Territory, Australia.
In the context of gold processing, sulfide minerals—such as pyrite, pyrrhotite, or arsenopyrite—can render gold-bearing ores "refractory" by physically encapsulating the gold particles. This physical barrier prevents the cyanide leach solution from making contact with the gold, thereby inhibiting the extraction process.1
To overcome this, the interfering sulfides must be destroyed to free the gold for subsequent cyanidation. Common methods include:1
- Roasting: Heating the gold-bearing minerals to temperatures between 450° and 750° C (840° to 1,380° F) to oxidize and destroy the sulfides.1
- Autoclave treatment: Utilizing high-pressure reactors called autoclaves to treat the minerals in an aqueous slurry with oxygen-bearing gases at high temperature and pressure.1
Once these oxidizing processes have successfully broken down the sulfide matrix, the gold becomes accessible to the cyanide solution for solubilization and recovery.1