Gold extraction is the extraction of gold from dilute ores using a combination of chemical processes. Gold mining produces about 3600 tons annually, and another 300 tons is produced from recycling.
Since the 20th century, gold has been principally extracted in a cyanide process by leaching the ore with cyanide solution. The gold may then be further refined by gold parting, which removes other metals (principally silver) by blowing chlorine gas through the molten metal. Historically, small particles of gold were amalgamated with mercury, and then concentrated by boiling away the mercury. The mercury method is still used in some small operations.