As gold investing becomes more popular, many investors are choosing to learn more about gold extraction to get a better grip on how the industry works and perhaps gain a competitive edge from this knowledge.
When gold is mined, it’s dug up in ore, that is gold metal mixed with other materials. Gold extraction is the separation of the precious metal from other materials in the ore. There are several methods used in gold extraction, including comminution, hydrometallurgical and pyrometallurgical processes and mineral processing.
Perhaps the easiest and most cost effective method of gold extraction is gravity separation. This technique was used by early miners to separate gold on placer deposits in river beds. Because gold has a heavier density, it tends to separate well when run through a gravity circuit.
Froth floatation is often used for gold extraction. In froth floatation, the ore is ground up an placed in water. A substance is added to the water that binds to the gold and helps it separate from the other materials.
Most modern mines use cyanide leaching as the main method of gold extraction. Cyanide is, in fact, responsible for most gold extracted in modern times. This process is costly and does pose a cyanide poisoning risk to workers, however.
In gold cyanidation, the ore is ground down and comminuted using froth floatation and gravity concentration. Once an alkaline ore slurry is formed, the processor will combine the slurry with cyanide. The pH of the solution used in extraction will be kept at an alkaline level pH to prevent hydrogen cyanide from being released, which can injure gold processing employees. The process can be sped up by the incorporation of lead nitrate.
About 90 percent of all gold extraction is done by cyanidation. This practice is often criticized because of its potentially fatal impact on human health and ill effects on the environment. Cyanide spills can have severe impact on the environment, just a small spill can kill significant amounts of fish and wildlife.
Some gold ores are “refractory” ores, which are resistant to cyanidation. These ores must be processed by different means including roasting, bio-oxidation, pressure oxidation and ultra-fine grinding.
In roasting, the sulfur and organic carbon present in gold ore is oxidized by using air and oxygen and heat. The bio-oxidation process uses bacteria to encourage oxidation in a liquid environment. Pressure oxidation uses an autoclave to process the ore using high pressure and heat. Ultra find grinding is, as the name suggests, the very fine grinding of gold ore to remove gold particles.
High costs for processing gold can have an impact on the price of gold, so as easily processed gold becomes increasingly scarce, and it gets more difficult to process mined gold, you can expect to see that difference reflected in the price of gold.
