Gold metallurgy — Apparatus. Industrial cases. Costs

Industrial cases testify to complex operations often combining mineralurgy, pyrometallurgy and biohydrometallurgy. However, heap leaching has been gaining ground for over twenty years, and has recently been replaced by biotreatment.

In dynamic leaching, gold ores are treated by a range of specific equipment, including mechanical, pneumatic and mechanopneumatic agitators to ensure contact between the leachant, oxygen and metal when the gold is accessible, and large-scale autoclaves working under oxygen pressure when the gold is combined with sulfides or carbonaceous materials.

Treatment costs decrease linearly with daily tonnage. When heap leaching is possible, costs are significantly lower, and capital expenditure is greatly reduced. Most industrial plants were built on the basis of a gold price of $350/ounce. On this basis, the average cost of worldwide mine-metallurgical production was $195-210/ounce in 2004.

When purchasing a gold mine and metallurgical plant, the overall value is between $70 and $100 per ounce of gold contained in the ore. It can be depreciated if the "golden" metal contains impurities that are troublesome for the refiner, and if there are political risks. Current strategies are geared towards obtaining rich pre-concentrates before the cyanidation stage.