Before we understand the difference between 24k, 22k, and 18k gold, you need to know what the term karat means. Carat is basically a unit used to measure the purity of gold. The higher the “caratage”, the more gold there is in your jewelry: it is therefore purer. Be careful, however, do not confuse the carat of gold with the "carat" as a unit of weight for weighing diamonds and precious stones. What is important to know, therefore Carat in jewelry is a unit of measurement (a proportion, a percentage) cut into 24 equal parts. Each share (carat) is equivalent to approximately 4.17%. Carat in gemology is a unit of weight (as can the kg). 5 carats in g is equal to 1 gram. Carat is then a term used in two very similar sectors, but whose meaning is totally different. In jewelry, the purest is 24 carats, while there is strictly speaking no limit in gemology. For example, the heaviest diamond ever discovered (the Cullinan, in South Africa) weighs 3,106 carats, or 621.2 grams
