How Is Gold Produced?
Main Gold Producing Countries
The main gold producing countries in the world are South Africa, the United States and Australia in that order. According to the United States Geological Survey, Nevada is the leading gold-producing state in the U.S. Other top gold producing states include Alaska, California, Colorado, New Mexico and Utah.
The largest part of gold in the United States is produced at above ground surface in open pit mines, even though mining and production methods and techniques are different depending on the location.
How Gold is Produced
There are the general steps in open-pit gold mining. The specifics of the process differ from mine to mine.
- Geologists utilize the most recent technology, such as satellite surveys and geochemistry, to locate an ore deposit.
- Computers are utilized in order to design the mine, and this entails accurate and precise measurement of the ore deposit. Construction starts after the extensive process of receiving permits.
- Samples of ore are then examined so as to settle on grade and metallurgical characteristics. Broken rock is marked according to the type for proficient processing.
- Depending on the metallurgical structure, a dispatcher directs truck operators to take the ore to the right processing site.
- Low grade ore is roughly broken into little pieces and put on carefully lined pads where a dilute cyanide solution has been dispersed over the top of the heap. The solution penetrates through the heap causing the cyanide to dissolve the gold. This solution that has the dissolved gold is then collected.
- High Grade Ore is then taken to a grinding mill, and in this place the ore is pulverized down to a powder. Depending on its metallurgical characteristics, the ore might be treated in one of three different recovery circuits:
- Refractory ore that has carbon is roasted to over 1,000 degrees Fahrenheit, and this burns out the sulfide and carbon. The result of this process is an oxide ore, and this is then routed to the discharge circuit.
- Oxide ore is sent straight to the discharge circuit where cyanide then takes care of dissolving the gold
- Sulfide refractory ore devoid of carbon is oxidized in an autoclave to release the gold from sulfide minerals, and then it is taken to the discharge circuit.
- Treated, high-grade ore is leached along with cyanide.
7. The gold is taken out of the solution onto activated carbon. The left behind cyanide solution is then recycled.
8. The gold loaded carbon is placed inside a container where the gold is then chemically stripped from the carbon that then must be recycled.
9. Gold is precipitated from the solution electrolytically or by means of chemical substitution.
10. The pure gold is then melted into bars that have up to 90 percent of gold. These bars are then sent to another refinery to be refined to bars of 999.9 parts per thousand pure gold.
Gold is produced at some mines like part of the process of mining and refining other metals, such as copper. At those operations, gold is refined to a suitable purity as part of the copper production process. At most gold mines, the gold is sent to a refinery for more processing.