Carat weight for gemstones
The international gem industry generally uses the term 'carat' as a unit of weight. Carat (sometimes abbreviated to ct. and also known as karat) have been used as a unit of measurement in gem trading since ancient times. The word is probably derived from 'kuara', the seed of the African coral tree. A carat is subdivided into decimal fractions (e.g. 0.75 ct) to two decimal places. Carat weight for gems should not be confused with carat as a measure of purity for gold.
Carat purity for gold
In gold jewellery, the carat is not a unit of weight but a designation of quality. The higher the number of carat of a piece of jewellery, the higher its proportion of pure gold. Two pieces of jewellery may therefore have the same number of carat yet differ widely in weight.
The carat rating of gold describes its purity and is expressed in fractions of 24 or 1000. Theoretically, pure gold contains 24/24 parts of gold – in other words, 1000 parts.
Jewellery makers work with alloys, mixing gold with other metals to achieve the desired colours and degrees of hardness. For example, highly coveted rose gold is made by mixing copper with pure gold.
Premium jewellers generally use alloys with the following proportions of pure gold: 750 gold = 18 carat and 585 gold = 14.04 carat.
At RenéSim we use by default 18-carat gold, containing 750 parts per thousand of pure gold.