About The Carat: Unit of Measure of Diamonds

The carat being the universal standard of weight and size for the diamond, a few remarks on this unit of the measure may here be found useful. The original meaning of this term has afforded subject for much controversy. Mawe cuts the matter short by asserting that the carat is an Indian denomination of weight. One hundred and fifty carats and a quarter are equal to an ounce troy (Op. cit. p. 2). But the carat, which is a Greek word, could not have been originally used as a denomination of weight in India, where the rati seems to have been the most general, though by no means a uniform standard. It fluctuated in different times and places between 1.86 & 2.25 grains, whereas the carat has the great advantage of being very nearly a constant factor everywhere. It is equivalent to 4 grains avoirdupois, five of which are equal to 4 grains troy, so that one carat is equal to 3.174 grains troy, and 151 1/2 carats to one English oz. The actual value of the carat in different countries, in milligrams, is as under:--

England 205.4090

France 205.500

Berlin 205.4400

Vienna 206.1300

Holland 205.044

Spain 205.3930

Portugal 205.7500

Brazil 205.7500