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How Many Carats?

You may hear the term carat being used a lot in watch manufacturing, and when you browse internet sites or peruse jewellers and retailers you will often find carat applied to two things; the gold (or platinum) metal used in the construction of the timepiece and also used when describing gems or pearls. This is because this is a word with two meanings, both of which are applicable to horology; meaning the purity of gold or platinum and meaning the mass of precious stones or pearls.

Carat is used less frequently to describe pearls or precious stones as it is precious metal purity; however occasionally horologists do use it as a means of defining the luxury of one of their models so it is worthwhile taking the time to understand exactly what carat means in this context. Carat (purity) is often abbreviated to either ct or K and occasionally you may see the alternative spelling karat in certain parts of the world to differentiate it from the other definition of the word. Strictly defined one carat will equal one twenty-fourth purity by the total mass of the gem or pearl. So for instance 24 carat gold is completely pure, 18 carat gold is 75% gold, 12 carat gold will be 50% pure, 9 carat gold will be 37% pure and so forth. Exactly the same measurements apply when measuring platinum, and when you have anything other than 24 K gold the other materials will simply be a mixture of relatively worthless alloys. Do not always be fooled into thinking that for ultimate luxury you must have 24 carat gold; in certain pieces of a watch it would not be wise to use pure gold as it is very soft and malleable and would likely get damaged very easily, so alloys are added to the gold and the gold is lowered to a new carat rating to provide toughness. Generally speaking the finest gold comes from the Far East (China, Taiwan) who produce “Chuk Kam” 24 K gold that is certified as such to within a 1% tolerance. India and the Gulf produce 22 K and 21 K respectively with a small amount of 18 K. 18 carat is also produced in the Southern Mediterranean area of Europe. Europe and the USA produce anything from 8 to 18 K and Russia now produces fine quality 14 carat. All gold (and platinum) will be hallmarked in some way, usually on the reverse of the watch dial in horology, and this will tell you the exact carat value of the gold used in its construction.

Carat (mass) is defined as a unit of mass used of measuring the weight of gems and pearls and is equal to exactly 200 milligrams. You will see this used less often in horology as it is simply a measure of mass and it is often easier for watchmakers to tell people the weight of the precious stones and pearls in other units such as grams or milligrams that are more easily understood. The word takes its roots from the carob seed which is found profusely in nature and was used in ancient times as a weight on precision measuring instruments as it was believed that all of the carob seeds had a naturally uniform weight. Of course this turned out not to be true when tested in modern times however the tradition has stuck, and it is still used as a measure of mass.