Shakudo (赤銅) is an alloy composed of Copper (Cu) (93~98%) and Gold (Au) (2~7%) (Shakudo can have other metals in it, though their content is usually <1%). Its melting point is 1900°F. Shakudo is a durable metal most noted for purplish-black patina (coloration, tarnish). The color comes from the metallurgical properties, not from any use of a coloring solution (as is common in European colored metals). This property is used aesthetically for creating a contrast with inlays (most notably pure gold), primarily to decorate katanas. Shakudo was primarily made in Japan. The alloy was generally unknown to the West until the 19th century CE, though similar alloys have been found in ancient Egypt, ancient Greece, and Rome.