What is carat?

Autor: Piotr Zieliński

When we consider buying jewellery, we focus first on the shape, colours and material used. However, after a while we look at the more detailed parameters. This is where the mysterious carats come in. What are they and how can they help us evaluate a given product?

A carat is a unit of mass that describes the weight of a gemstone. The international symbol for this unit is ‘ct’. The name carat comes from the French word "caraton" meaning carob fruit, or carob tree. The seeds of this plant have been used for centuries in the Middle East to determine the weight of gemstones. As they weighed about 0.2 g, it was assumed that 1 ct = 0.2 g. A properly cut brilliant, weighing 1 ct, has a diameter of about 6.3 mm.

585 or 14K gold?

Interestingly, this unit is also used to determine the purity of gold. However, in this case, the symbol is 1K. In this case the carat does not mean the weight, but the proportion of gold in relation to the other metals in the alloy. Pure gold is assumed to be 24 carats, which means that 24 parts of the alloy are 24 parts gold. So, for example, in 14k gold, the precious metal is a 14/24 alloy.

In Poland, a percentage of the sample is used. 14K gold contains 58.5% of the precious metal, hence the Polish designation of this alloy is 585. Below I present a list of examples with the most popular alloys:

24-carat - 999 - 99.9% AU
22-carat - 960 - 96.0% AU
18 carat - 750 - 75.0% AU
14-carat - 585 - 58.5% AU
12-carat - 500 - 50.0% AU
10-carat - 417 - 41.7% AU
9 carats - 375 - 37.5% AU
8 carats - 333 - 33.3% AU