Amal'gam, an alloy or mixture of mercury and some other metal. The principal amalgams are with gold, silver, tin and copper. These alloys are most commonly formed by bringing mercury into contact with the other metal. In metallurgy mercury is used to extract free gold and silver from their ores because of its power of uniting with these metals. Tin amalgam is used for silvering mirrors. Copper amalgam has the power of softening when worked and becoming hard on standing; consequently it has been used for filling teeth.