Leaching
If the gold can not be concentrated for smelting, then it is leached by an aqueous solution:
- The cyanide process is the industry standard.
- Thiosulfate leaching has been proven to be effective on ores with high soluble copper values or ores which experience preg-robbing: the absorption by carbonaceous components which preferentially absorbs gold and gold-cyanide complexes.
Read more about this topic: Gold Extraction