Carat

The unit of weight for a diamond or other gemstone and also for a pearl. Abbreviated ‘ct’, 1 carat is equal to 0.2 grams.

In reference to gold, a unit of purity or fineness of gold and gold alloy, expressed as a number out of 24 parts by weight, e.g. ’24 carat’ signifies pure gold, ’18 carat’ 18/24th gold in the alloy, et cetera.  Also abbreviated as ‘ct’.

Originally derived from the carob seed, called quirat in Arabic, a seed of naturally uniform weight.