The carat is a unit of measurement of the weight (more precisely of mass) of precious stones and especially diamonds. Today it corresponds to exactly 0,2 grams (1/5 of a gram or 0.007055 oz). In the past, each country had its own definition and legal framework for the "carat", a fact that to this day creates a lot of confusion.
The word "carat" comes from the Greek word horn, which refers to the seeds of the carob tree (Ceratonia siliqua). Because carob seeds have the ability to be quite uniform in size and keep their weight unchanged, regardless of external conditions, the goldsmiths and silversmiths of Venice used them as a unit of weight to measure the weight of precious stones and metals. At that time anyone could buy some corneal seeds in the market and weigh the valuable commodity for verification. This plant thrives throughout the Mediterranean region, in the Arab countries and India.
