Heap leaching is a hydrometallurgical extraction process widely used in the mining industry to recover valuable metals from low-grade ores. The technique is particularly common in gold mining but can also be applied to other metals. In this process, crushed ore is stacked in large heaps on an engineered, impermeable pad lined with synthetic materials to prevent leakage into the surrounding environment. A chemical solution, known as the leaching agent, is sprayed or dripped onto the heap. As the solution percolates through the ore, it dissolves the target minerals and carries them downward to a collection system. The metal-bearing solution is then processed to recover the valuable metal.
In gold mining, cyanide solutions are commonly used to dissolve gold particles, while other mining operations may employ sulfuric acid or different reagents depending on the mineral being extracted. Heap leaching offers significant economic advantages because it enables the processing of low-grade ore that would otherwise be uneconomical to mine. The method requires relatively low capital investment compared to conventional milling and smelting operations.
However, heap leaching requires careful design and environmental management. Factors such as ore permeability, particle size distribution, solution chemistry, climate, and heap height influence recovery efficiency. Modern heap leach facilities incorporate monitoring systems, leak detection technologies, and solution containment measures to minimize environmental risks. In large-scale gold operations, heap leaching has become one of the most cost-effective and widely adopted methods for metal recovery.