A noble, heavy, ductile, malleable yellow-colored metal and a chemical element with the symbol Au (from the Latin Aurum).The metal occurs in the native form as nuggets, grains and specks in rocks and alluvial deposits. Pure gold is very malleable to be worked normally; it is therefore hardened by creating alloys with other metals (usually copper and silver). When it is an alloy with other metals, the purity is measured in carats or millesimal fineness, on a scale that sets pure gold at 24 carats or 999,9999 millesimal fineness. The gold used in jewelry production by European countries is mostly produced with a maximum purity of 18k or 750 millesimal fineness. Gold has been known and very much appreciated since prehistoric times. It was probably the first metal ever used by the human species (even before copper), for ornaments, jewelry and rituals. Other leading producers include the United States (mainly in South Dakota and Nevada), Australia (mainly in Western Australia), as well as Peru and Russia.