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60
PRECIOUS STONES.

the locust-tree, Ceratonia siliqua, weighs on the average 31/6 grains, and constitutes, no doubt, the true origin of the carat.

The carat is not absolutely of the same value in all countries. Its weight, as used for weighing the diamond and other gemstones in different parts of the world, is given, in decimals of a gram, by the majority of the authorities, as—

Madras ·2073533 France ·2055
Vienna[1] ·20613 England ·205409
Frankfort ·20577 Spain ·205393
Brazil and Portugal ·20575 Holland[2] ·205041

Assuming the gram to correspond to 15·43235 English grains, an English diamond carat will nearly equal 3·17 grains. It is, however, spoken of as being equal to 4 grains, the grains meant being "diamond" grains, and not ordinary troy or avoirdupois grains. Thus a diamond grain is but ·7925 of a true grain. In an English troy ounce of 480 grains there are 1511/2 carats; and so it will be seen that a carat is not indeed quite 3·17 grains, but something like 3·1683168 grains, or less exactly, 3·168 grains. Further, if we accept the value in grains of one gram to be, as stated above, 15·43235, and if there be 1511/2 carats in a troy ounce of 480 grains, it will follow that an English diamond carat is ·205304 of a grarn, not ·205409, as commonly affirmed. By recalculating the value of the diamond carat, as used in different parts of the world, into its scientific equivalents in the metric system, the weight to four places of decimals will become, according to Mr. Lowis D'A. Jackson[3]

Turin ·2135 Holland and Russia ·2051
Persia ·2095 Turkey ·2005
Venice ·2071 Spain ·1999
Austro-Hungary ·2061 Java and Borneo ·1989
France ·2059 Florence ·1965
Portugal and Brazil ·2058 Arabia ·1944
Germany ·2055 Egypt ·1917
England and British India ·2053 Bologna ·1886

  1. Schrauf gives·2057.
  2. Schrauf gives ·20613.
  3. Modern Metrology, p. 377.