Everyone is familiar with the term "carat" when talking about either gold or precious stones. However, not everyone is aware that carat as applied to gold, means something completely different to carat as applied to diamonds.

Precious Stones
In this context, a carat is simply a measurement of weight (1 carat = 0.2 grams). Hence the more carats, the heavier the weight and, other things being equal, the greater the value. Of course, in real life other things never are quite equal, so the value of the stone includes other factors such as clarity, colour, the quality of the cutting, even the country of origin.

If you were wondering where the term carat originated, it derives from "carob" - as in the food ingredient sometimes used instead of chocolate. In ancient times precious stones were measured according to the weight of carob seeds (one carob seed equals one carat).

Carat – Gold
In this case, the number of carats (also written as karats) equates to the proportion of gold, up to a maximum of 24. Hence an item which is 24 carat gold is 100% gold, although 24 carat gold is rarely used for jewellery as it is very soft and easy to damage. Other metals are usually added and it is the proportion of these other metals which defines the number of carats. Hence an 18 carat ring is 75% gold and a 9 carat ring is 37.5% gold.

In fact, an international numbering system has replaced the carat system, at least as far as the trade is concerned. Its technical term is “millesimal fineness” which is a slightly pompous way of saying how much gold there is per thousand parts of the metal (mille being 1000). Pure gold is 1000°, while 18 carat gold is 750°, 14 carat gold is 585° and so on.