amalgam

Any alloy of mercury with other metals. Most metals will form amalgams, except iron and platinum. Amalgam is used in dentistry for filling teeth, and usually contains copper, silver, and zinc as the main alloying ingredients. This amalgam is pliable when first mixed and then sets hard, but the mercury leaches out and may cause a type of heavy-metal poisoning.

Amalgamation, the process of forming an amalgam, is a technique sometimes used to extract gold and silver from their ores. The ores are ground to a fine sand and brought into contact with mercury, which dissolves the gold and silver particles. The amalgam is then heated to distil off the mercury, leaving a residue of silver and gold. The mercury is recovered and reused.

Amalgamation to extract gold from its ore has been in use since Roman times.

Tin amalgam is used for backing mirrors, and gold and silver amalgams are used for gilding purposes.