When visiting a jewellery shop, many people have heard the term “carats”, without actually knowing what it refers to. Certainly, something that is widely known is that the more karats a piece of jewelry is, the more valuable it is. But what are carats and how are they measured?
Carats: the mass of a gemstone
Carat weight is essentially an expression of the mass of a gemstone. If we had to express it in weight, a carat is equivalent to 0.2 grams. The symbol used to denote a carat is the abbreviation ct. As a unit, it is divided into subunits, where points are the subunits. To help you understand the ratio better, here are some basic facts:
One carat = 1.00ct = 100 points
Half a carat = 0.50ct = 50 points
1 point = 0.001ct
What does Ct and K stand for in jewellery?
As mentioned above, the ct symbol is used to denote carats. The term karat, however, is also used for gold. In that case it is a different unit of measurement as it expresses something different compared to all other jewellery. In particular, for gold jewellery it expresses the gold content of a metal alloy. The symbol in this case is K (Karat). This is why in product descriptions you will see different symbols each time.
A few words about carats
The word karat is derived from the Arabic “qirat”. This in turn is borrowed from the Greek word “keration” which refers to the carob plant (Ceratonia siliqua), a plant that thrives in the Middle East, the Mediterranean and India. In earlier times, carob seeds were used to measure the weight of precious stones. This was because they were uniform in size and relatively constant in weight. So in traditional scales, the goldsmiths of the time would place the stones on one side and counterbalance them with carob seeds, each of which was equal to 1ct.
Of course today, electronic precision scales are used to measure the weight of the gemstones in millimetres of carat. The result is then rounded off to centimetres of carat following specific international regulations.
Eva Kountourakis GG, AJP, JBM
Gemology Instructor, Jewellery Consultant
