The Cyanidation of Gold:
The figure shown below schematically describes the process used at Barrick's Goldstrike Property.
It includes two grinding circuits, each composed of semi-autogenous grinding (SAG)
and ball mills, which grind the ore into a fine particle slurry. The ore is "refractory" meaning that the gold is
locked in sulphide minerals and thus sulphide pre-treatment is required. To
improve the recovery rate an extra process step, pressure oxidation ("autoclaving"),
occurs after the milling and before leaching. Autoclaving oxidizes the sulphide minerals and exposes the gold particles,
improving gold recovery to 90%. After neutralization, a
carbon-in-leach system is then used to extract the gold from the oxidized slurry.
In the final gold recovery and refining phase, gold is stripped
from the carbon and poured into doré bars.
Also available is information on the Goldstrike Roaster (scheduled for full operation
by mid-2000), and on Heap Leaching in Pierna.
Click on any circuit in the process (designated by colour) to view a description of that stage.
Description: Also online are descriptions of Barrick's
five mines in North and South America.