Britannica Sources used in this answer

How does heap leaching recover gold from low-grade ore?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A worker in safety gear walks beside a conveyor belt carrying ore at the Tanami gold mine in the arid, expansive landscape of the Tanami Desert. — gold processing The Tanami gold mine, Northern Territory, Australia.

Heap leaching is an efficient method used to recover gold from low-grade or semilow-grade ores that are brought to the surface for processing.12

The process involves piling crushed ore onto prepared pads to form large heaps. These heaps are then sprayed with a dilute sodium cyanide solution. As the solution trickles or percolates down through the piled ore, it dissolves the metallic gold. The resulting gold-bearing, or "pregnant," solution is then drained away from the base of the heap and collected for further treatment in precipitation tanks to recover the gold.12

This technique is particularly valuable because it avoids the high capital costs associated with the complex solids/liquids separation equipment required for vat leaching, making it an economically viable way to process large tonnages of low-grade material.1