Gold extraction

Gold revcovery from its ores may require a combination of comminution, mineral processing, hydrometallurgical and pyrometallurgical processes to be performed on the ore. Once the ore is mined, it can be treated as is using a dump leaching or heap leaching process.

In the case that the ore is not economically suited to dump leaching or heap leaching processes, either because it is of high grade or refractory to cyanide leaching at coarse particle sizes, commuinution is used to crush and grind the ore into finer particles. Gravity concentration or froth flotation processes may be used to concentrate the gold. In some cases, a gravity concentrate can be direct smelted to form gold bars. In other cases the concentrates are subjected to intensive cyanidation leaching, followed by recovery from gold in solution by carbon in pulp or electrowinning. If the gold is present as a minor consituent in a base metal concentrate, it can be recovered in the anode slime during the electrorefining process.

Cyanidation

If the gold is not concentrated, then it is leached by cyanide solution.

Refractory Gold Processes

If the gold is trapped inside minerals which are not pourous, and so the gold is not liberated to the leach solution, then a refractory gold treatment step may be required before cyanidation. These include:

 i) Concentrate or whole ore roasting
 ii) Concentrate or whole ore bio-oxidation
 iii) Concentrate or whole or pressure oxidation in autoclaves
 iv) Ultrafine grinding