How was mercury once used to extract gold and silver from ores?

Mercury was historically used to extract gold and silver through a process known as amalgamation, which exploits the fact that these metals are soluble in mercury. When gold or silver particles come into contact with a fresh mercury surface, they are wetted and dissolved to form an alloy called amalgam.12

Methods of amalgamation included:
* Direct contact: Passing ore slurry over mercury-coated copper plates or mixing it with mercury in vessels like barrels or grinding mills.1
* The Patio Process: Used extensively for silver, this involved grinding ore into a fine mud, spreading it on a patio, and mixing it with mercury, salt, and copper sulfate.3

Once the metals dissolved into the mercury, the resulting amalgam was separated from the barren ore. The mercury was then recovered for reuse by heating the amalgam in a sealed retort to distill it off. While effective, this practice poses severe ethical and environmental concerns due to the high toxicity of mercury, which can cause mercury poisoning in operators and contaminate ecosystems.1345