The 4Cs of the diamond: the Carat
Diamonds are precious stones of immeasurable value, so important and special that they are assessed according to 4 "C"s: carat weight, purity, colour, cut.
Today, let us look together at the first of the 4 Cs: what are carats?
First of all
A carat is a unit of measure, used in metallurgy and goldsmithing to define the mass of precious materials. It can also be an indicator of the purity of gold alloys.
The weight, expressed in carats, is the measure of the mass of a diamond. One carat corresponds exactly to 200 milligrams.
The history
The carat has been used as a unit of measure for weighing very small quantities since ancient times. After the Middle Ages, it remained the unit of weight measurement concerning the world of precious stones. It therefore applies to diamonds, stones and gems, and to the purity value of gold.
The actual definition of the carat weight was established in 1832, in South Africa. At the time, the region was the world’s largest producer and exporter of diamonds. It was there that the exact relationship between carats and metric system measures was set: some carob seeds were weighed on a balance scale with equal arms to calculate an arithmetic mean with the measured diamond: the value was about 0.2 grams. The carat value was officially confirmed in 1907, at the General Conference on Weights and Measures.
1 Carat = 0.2 Grams
The name
The word derives from the Arabic qīrāṭ, meaning “twenty-fourth part.” The Arabic word seems to come in turn from the ancient Greek κεράτιον (kerátion), referring to the seed of the carob tree, which were believed to always have a constant mass.
In reality, the mass of these seeds varies, as happens with all seeds in the world. However, since ancient times they were used as a standard of comparison because it was easy to notice the difference in size with the naked eye, thus choosing seeds that had the same weight.
The carat and gold
Regarding gold alloys, the term carat takes on a different meaning from the unit of weight proper to gems and pearls, becoming a measure of purity, which quantifies the parts of gold in an alloy on a 24/24 basis. A carat, therefore, when speaking of gold, means the part of gold out of a total of 24 parts of metal making up the alloy. The highest purity gold is thus 24 carats.
Why is the reference number for purity 24? There is an explanation for this too: it comes from an ancient pure gold coin used thousands of years ago in Germany. This weighed 24 carats, that is 4.8 grams. Its composition and weight were taken as a reference point to assess the purity of gold jewellery.
A jewel with 24 carats (generally expressed as 24K) is the purest on the market, because it corresponds to 999.9 grams of gold per 1000 grams. This type of gold is not used because gold is soft and tends to deform easily.
Below are other marks that can be found engraved on a jewel. The most common, from the most precious and costly, are:
- 22 Kt (916.667/1000) – over 90% gold
- 18 Kt (750.000/1000) – 75% gold
- 12 Kt (583.333/1000) – 50% gold
Most gold jewellery found in the European area is 18 Kt, where gold is present at 75%. By law, every gold jewel should have an engraving on its surface indicating the maker’s name and the carats: in the case of 18K, this equals 750.
The carat is the unit of measure that characterises the weight of a diamond. The more carats it has, the more precious the diamond in question!
