Gold is measured in karats. Karat is the percentage of gold per thousand that a piece of jewellery contains. So, 9 karats are 375/1000, 14 karats are 585/1000 and 18 karatsare 750/1000. It is mandatory for every piece of jewel to have a stamp stating its karats, as well as a stamp of the construction workshop. This provision is valid worldwide. Karats should not be confused with the unit of measurements of precious gemstones. Although similar, the unit that measures the size of precious gemstones is Carats instead.