Carat
The carat is a unit of mass used for measuring gemstones and pearls. One carat equals 200 milligrams (0.2 grams). It should not be confused with 'karat,' which measures the purity of gold.
History
The word 'carat' derives from the Greek 'keration,' referring to carob seeds that were historically used as counterweights on balance scales due to their uniform weight. The modern metric carat of 200 mg was adopted internationally in 1907.