mercury and one or more other metals .
Those of silver, gold, and palladium occur naturally. Those with a very high mercury content are liquid; others are crystalline. Amalgams of silver and tin, with minor amounts of copper and zinc, are used in dentistry to fill teeth. Sodium amalgam is used in manufacturing chlorine and sodium hydroxide by electrolysis of brine. Amalgams are used to recover silver and gold from their ores: The ore is shaken with mercury, the amalgam is separated and heated until the mercury distills off (see {{link=distillation">distillation ), and the precious metal is the residue. Amalgams are also used to silver mirrors and apply other metal coatings.