Process for recovery of gold from refractory ores

In a process for the recovery of gold from a refractory auriferous ore containing sulfide sulfur, which ore may contain natural carbonate, wherein a slurry of the ore is oxidized with oxygen gas under pressure in the presence of sulfuric acid, the oxidized slurry is neutralized, the neutralized slurry is cyanidized to leach gold therefrom, and gold is recovered from the resultant leachate, and wherein the rate at which sulfuric acid is added to the ore slurry is controlled so that, after a startup phase, the amount of sulfuric acid added to the ore slurry is sufficient to insure oxidation of that portion of the sulfide sulfur in the ore which will allow recovery, by cyanide leaching, of at least about 80% of the gold in the ore, the improvement which comprises:

• cooling the oxidized slurry and passing the cooled slurry directly to a neutralization operation wherein the slurry is neutralized with a base which forms a substantially insoluble salt on neutralization with sulfuric acid.