It is performed in an autoclave at high pressure and temperature, where high-purity oxygen mixes with a slurry of ore.[2] When the original sulfide minerals are oxidized at high temperature and pressure, it completely releases the trapped gold.
The iron-based solids produced pose an environmental challenge, as they can release acid and heavy metals to the environment.
Arsenic in the ore is converted to solid scorodite inside the autoclave, allowing it to be easily disposed of.
At Pueblo Viejo, the process is performed by injecting high-purity oxygen into autoclaves operating at 230 degrees C and 40 bar of pressure.
[3] The oxidation of pyrite is highly exothermic, allowing the autoclave to operate at this temperature without an external heat source.