text: However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloys mass consists of 75% of gold and 25% of other metals. The quantity of gold by volume' in a less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm for gold, 10.49 g/cm for silver and 8.96 g/cm for copper.