The valuable precious stones are bought and sold by the carat. This
weight is equal to about 3.17 grains or about .205 milligrams.
The carat is divided into fractions of ½, ¼, ⅛, 1/16, 1/32, 1/64, and
also arbitrarily into four grains; that is, each quarter of a carat is
counted one grain, thus forming the basis for the calculation of pearls.
In commerce, a carat diamond is sometimes called a four-grain stone,
and a carat-and-a-half stone is six grains, etc., etc.
The weight of the carat being arbitrary, it varies in different
countries, some being heavier and others lighter than .205 milligrams.
The writer wrote to three prominent balance-makers in the United
States some months ago for their carat standards and was surprised to
find that they all differed. This will account for discrepancies in
weight resulting between the balances of different makers. Of late
there has been a decided movement in Europe, headed by the French
Chambre Syndicale of jewelers, in favor of the unification of the
carat, so that the weight of a French or Dutch carat will equal that
of an English, American, or any other carat. This reform will probably
be accompanied by the adoption of the decimal system of dividing the
carat, and the discarding of the complicated fractional system.
After having tried the decimal weights for many months, the author can
testify to a decided gain in time and accuracy from their use.