Processing, smelting and refining gold | World Gold Council
With ores of higher gold content (greater than 20 grams of gold per tonne of ore), cyanidation is accomplished by vat leaching, which involves holding a slurry of ore and solvent in large tanks equipped with agitators. For extracting gold from lowgrade ores, heap leaching is practiced; huge heaps are sprayed with a dilute solution of sodium cyanide, and this percolates down through the piled