Refining is the process whereby a pure metal is extracted from a mass containing other elements or impurities. The term applies to the process of extracting gold, silver, and platinum from their ore as well as purifying existing precious metal alloys. These two applications require different methods. Existing alloys can be purified by dissolving them in acid after which the individual components of the alloy are allowed to recrystallize separately. Extraction from ore involves a lot more waste material so this is done in an industrial manner.