Chemicals Used to Extract Gold From Ore

Gold has many uses in fashion items and industry.

The first recorded use of gold was approximately 3600 B.C. in Egypt. Since then, gold has been used for many things, from jewelry to the plating of electronics to improve conductivity. Until the 1900s, countries around the world backed their currencies with gold, as citizens could exchange the money they held for physical gold. To fulfill these purposes, however, gold first must be extracted from its natural sources.

Mining Gold

Miners find gold in several ways. Erosion caused by water deposits gold from rocks into rivers and streams. Miners pan for minute amounts of gold from these sources. The majority of gold is extracted directly from rocks. After mining, trucks deliver the gold-laden rocks for processing. A chemical bath separates the gold from the rocks for collection.

Extracting Gold Using Cyanide and Carbon

One common chemical used to extract gold from rocks is cyanide. Cyanide acts as a solvent on gold. The ore containing gold is pulverized into small pieces and then piled up. A cyanide solution poured on the pile dissolves the gold. The gold solution collects on filters of activated carbon for processing.

Extracting Gold Using Mercury and Nitric Acid

Mercury amalgamation was developed in 1555. Pulverized gold ore is mixed in a slurry of mercury or run over mercury-laden plates. The amalgam of mercury and gold is collected and heated to burn off the mercury, or the mercury is dissolved in a solution of nitric acid.

Environmental Concerns

Cyanide and mercury are toxic chemicals. Organizations such as Fairtrade International and the Alliance for Responsible Mining work to ensure that conditions in gold mines do not exploit or otherwise harm miners. The Environmental Literacy Council monitors mines to make sure they prevent cyanide and other toxic chemicals from making their way into the environment.

References

• World Gold Council: About Gold
• National Mining Association: How Gold is Produced
• Arizona Department of Mines and Mineral Resources: Treating Gold Ores by Amalgamation
• Fairtrade International and the Alliance for Responsible Mining: Fairtrade and Fairmined Gold
• Environmental Literacy Council: Gold Mining

Resources

• Gold Fever Prospecting: Where to Find Gold in the United States