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Why are refractory gold ores difficult to treat with cyanidation?
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gold processing
The Tanami gold mine, Northern Territory, Australia.
Refractory gold ores are difficult to treat with cyanidation because they contain substances that interfere with the chemical process in three primary ways:
- Reagent Consumption: Certain minerals consume the cyanide reagent before it can effectively dissolve the gold.1
- Preg-robbing: Some materials preferentially adsorb the gold as it dissolves, preventing its recovery.1
- Physical Encapsulation: The gold particles may be completely surrounded by other minerals, such as the sulfide minerals pyrite, pyrrhotite, or arsenopyrite, which prevents the cyanide leach solution from accessing the gold.1
To overcome these challenges, these ores must first undergo oxidizing processes to destroy the interfering sulfides. Common methods include roasting the minerals at high temperatures or using high-pressure autoclaves to treat the ore slurry with oxygen-bearing gases. Once the oxidation is complete, the gold is liberated and can be successfully extracted using standard cyanidation techniques.1