Gold typically occurs at very low concentrations in ores – less than 10 g/ton. The most used process for gold extraction is hydrometallurgical recovery (gold cyanidation), which involves a "leaching" step during which the gold is dissolved in an aqueous medium, followed by the separation of the gold bearing solution from the residues.
Heap Leaching, Heap Leaching Consulting, Heap Leaching of Gold . Heap leaching (HL) is a flexible and economic mineral processing method, commonly used to extract gold from low grade gold ores. In this process, ore is firstly crushed to fine particles. By spraying leaching solution to the large piles, the gold containing solution is leached.