Standards – Carat

The purity of gold is now measured also in terms of fineness, i.e parts per thousand. Thus 22 carat is 22/24th of 1000 parts = 916 fineness.A Carat (Karat in USA & Germany) was originally a unit of mass (weight) based on the Carob seed or bean used by ancient merchants in the Middle East. The Carob seed is from the Carob or locust bean tree. The carat is still used as such for the weight of gem stones (1 carat is about 200 mg). For gold, it has come to be used for measuring the purity of gold where pure gold is defined as 24 carats.