Techniques to Extract Gold From Ore

Gravity Concentration Methods

• A common method of extracting gold from ore requires crushing the rock and then sifting it through sluices, jigs, spirals and tables. The crushed rock may be soaked with water, and the rock and gold then sent through a series of shakers and sifters. Gold is heavier than most materials and gets trapped in the bottom of these sifters. This is the lowest cost method of obtaining the gold, but may leave a fair portion of gold in the rocks themselves.

Flotation Process

• Crushed gold ore has a high concentration of sulfides. Miners will make a slurry of the crushed ore, add oil and mix with air bubbles. Sulfides do not become wet easily and so float to the surface for skimming along with the gold. The type of oil depends on the type of sulfides in the ore.

Cyanide Mill Process

• A very efficient method of gold extraction is dissolving the crushed gold ore in a weak cyanide solution. Gold dissolves in cyanide in special tanks, where the solution is mixed and aerated. The cyanide solution is then processed so the gold precipitates out of the solution in a large, shallow tank.

Heap Cyanide Process

• A less efficient way of extracting ore than the cyanide mill is the heap cyanide leaching process. The gold ore is placed on a liner and the cyanide solution is sprinkled on the gold ore. The gold leaches through the ore and is channeled to a man-made pond for holding and precipitation.