Carat weight is one of the four quality factors of gemstones. The carat is essentially the expression of the mass of a gemstone. One carat is equal to 0.2 grams, so 5 carats are equal to one gram. As a symbol of the carat the abbreviation ct is used.
The carat is divided into sub-units, the points. The division is similar to the euro and cents, so just as one euro is divided into 100 cents, so too is one euro divided into 100 cents: One carat = 1.00ct = 100 points, half a carat = 0.50ct = 50 points. One point 1 point =0,001ct
- Ct vs K
The term karat is also used for gold, but in that case it is a different unit of measurement and expresses the gold content of a metal alloy. The symbol for gold carat is K (Karat).
- History
The word carat is derived from the Arabic “qirat”, which in turn is borrowed from the Greek language and the word “keration” which refers to the carob plant (Ceratonia siliqua), a plant that grows in the Middle East, the Mediterranean and India. In earlier times, carob seeds were used as a unit of measurement of the weight of gemstones, as they were of uniform size and relatively constant weight. So in the traditional scales, the goldsmiths placed the stones on one side and as a counterweight they had carob seeds, each of which corresponded to 1ct.
Of course, today electronic precision scales are used to measure the weight of gemstones to the thousandth of a carat, which is then rounded to hundreds of a carat following specific international regulations.
Eva Kountouraki GG, AJP, JBM
Gemology Instructor, Jewellery Consultant
