Britannica Sources used in this answer

How do gold and silver form amalgams with mercury?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Mercury thermometer — mercury processing Mercury in the bulb of a thermometer.

Gold and silver form amalgams with mercury because they are soluble in the metal. When particles of gold or silver come into contact with a fresh mercury surface, they are wetted and dissolved, creating an amalgam—a crystalline or liquid alloy.12

This process is utilized in gold processing to recover fine particulate metals. It is typically achieved by:

Passing ore slurry over mercury-coated copper plates.13
Mixing ore and mercury in specialized vessels, such as amalgam barrels.1
Grinding ore in mills with added mercury to free the metals from their mineral matrix.1

Once the amalgam is formed, it is separated from the barren ore. The precious metals are then isolated by heating the amalgam in a sealed retort to distill off the mercury, which can be recovered for reuse.12

It is essential to note that while this method is effective for extraction, it poses severe risks of mercury poisoning to operators and the environment. Ethical practice demands the use of carefully designed, closed-loop equipment to prevent toxic contamination.14