Since it is a fixed mass of small seeds.
The term “carat” entered the jewelry practice in the 15th–16th centuries. It comes from the similar-sounding name of the carob tree (Ceratonia siliqua) in Mediterranean languages.
The seeds of this tree are known for their remarkable mass stability, which is approximately 0.19 grams. They were used as a small unit of weight measurement as far back as the Roman Empire.
Currently, the metric carat, equal to 0.2 grams, is used to determine the weight of gemstones and pearls.
