heapleachingin

Heap leaching is a mining technique used to extract metals from low-grade ore by stacking crushed ore on an impermeable liner and applying a leaching solution. It is widely employed for gold and copper because it can treat large volumes at relatively low capital cost, especially when ore quality is insufficient for more intensive milling approaches.

In the process, ore is blasted or excavated, crushed to a suitable size, and placed on a prepared pad or gallery with drainage and a liner system. A leachant, typically a cyanide solution for gold or sulfuric acid for copper, is distributed over the heap through sprinklers or drip systems. The solution percolates through the ore, dissolving the target metal. The pregnant leach solution is collected at the base in lined ponds or tanks for metal recovery. Gold is usually recovered by carbon-in-pulp, carbon-in-leach, or precipitation (Merrill-Crowe), while copper is recovered by solvent extraction and electrowinning (SX/EW).

Key considerations include ore permeability, strength of the pad liner, and the design of irrigation and drainage systems. Environmental and safety aspects are central: cyanide management, containment to prevent leakage, treatment of leachate, and rehabilitation of the site after mining ends. Heap leaching offers flexibility to process variable ore bodies and can minimize capital expenditure, but it also introduces longer processing times and heightened need for robust containment and monitoring to mitigate environmental risks.