Recycling is a part of the life cycle of materials and particularly metals. Some metals have been recycled for many decades. The re-use of metals such as steel, iron, aluminum and copper are proven to be economic and are regularly entered into the production stream of new materials. Precious metals are also regularly recycled, such as gold and silver (from electronics) and platinum and palladium (from catalytic converters). Recycling of many other metals is not easily accomplished economically or in some cases, is not even technically possible. When a metal is recycled, that quantity does not have to be mined.