An 18-karat gold alloy consists of this percentage of gold
75% 
Gold ... A tiny piece of metal is scraped from the piece and the percentage of gold 
or ... Electrum is also an alloy used in medieval times consisting of copper (50%),
... [DOC] [TLE] Gold and Gold Alloys :: Total Materia Article [PAR] Colored gold alloys are just as "real" as their golden colored counterparts.