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Mercury forms a mercury-gold amalgam with smaller gold particles, and then the gold is concentrated by boiling away the mercury from the amalgam. This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour. Large-scale use of mercury stopped in the 1960s.
Gold cyanidation (also known as the cyanide process or the MacArthur–Forrest process) is a hydrometallurgical technique for extracting gold from low-grade ore through conversion to a water-soluble coordination complex. It is the most commonly used leaching process for gold extraction. [1]
This makes the extraction of the non-radioactive isotope from spent nuclear fuel possible after a few years of storage, although the extract must be checked for radioactivity from trace quantities of other elements before use. [1] The radioactivity in MBq per gram of each of the platinum group metals which are formed by the fission of uranium.
This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour. [61] [64] Large-scale use of mercury stopped in the 1960s. However, mercury is still used in artisanal and small-scale gold mining (ASGM). [61] [65]
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Gold amalgam has proved effective where gold fines ("flour gold") would not be extractable from ore using hydro-mechanical methods. Large amounts of mercury were used in placer mining , where deposits composed largely of decomposed granite slurry were separated in long runs of "riffle boxes", with mercury dumped in at the head of the run.
Mercury is used in illegal gold mining to help separate gold particles from a mixture of sand or gravel and water. [103] Small gold particles may form mercury-gold amalgam and therefore increase the gold recovery rates. [13] The use of mercury causes a severe pollution problem in places such as Ghana. [103]
The silver separation process generally differed from gold parting and gold extraction, although amalgamation with mercury is also sometimes used to extract gold. While gold was often found in the Americas as a native metal or alloy , silver was often found as a compound such as silver chloride and silver sulfide , and therefore required ...