Mode of Buying and Selling.
The trade
in diamonds represents, perhaps, 90 per cent, of the capital invested
in precious stones, and there is not much likelihood of diamonds
depreciating in value at present, or the large amount obtained at the
mines of South Africa during late years would have had the effect of
much cheapening them, as the quantity taken from these mines since
their discovery is reckoned by tons, and as the output is likely to be
regulated, prices will probably be maintained.
Many
fluctuations in the value of diamonds have taken place during the
present century, brought about by extraordinary circumstances; as when
Dom Pedro paid the interest of the Brazilian State debt to England in
diamonds ; and again in consequence of the French Eevolution in 1848,
and other like instances. In 1750 the value of a diamond, based on the
brilliant and weighing 1 carat, was £8, a gem of 2 carats £32, one of 4
carats £128, and so on. This rule is from the tables of David Jeffries,
although it has been traced to 100 years before, and is based on the
square of the weight of the diamond in carats multiplied by 8, the
value in pounds of 1 carat; for example, a stone of 2 carats, 2 x 2 X
8= £32. There appears to have been no other tables yet compiled, and
although this mode of calculation gives a rough value, yet it is not
followed now, as the value of small brilliants of 1 to 4 carats has
increased out of all proportion to the gems of greater -weight, a
perfect gem of 1 carat being valued at nearly three times as much. It
is almost impossible to value a diamond by its weight alone, as so much
depends upon the colour, brilliancy, and cutting of the gem. Diamonds
of absolute purity, clear as water, and free from all blemish, are
called of the " first water," only about 8 per cent, of those found
being of tbis quality, while 25 per cent, are of the second quality.
Some authorities give the percentage of the best stones as higher than
here given.
The Carat and Sale of Gems.
Precious stones are purchased by a weight called a carat, a word
probably derived from a seed, of which there are several that have
nearly constant weights, and are native in India. The scarlet and black
leguminous seed Aimsprecatorius weighs about 2 grains, the seed of Adenanthera pavonina about 4 grains, while that of the locust tree, Ceratonia siliqua, weighs
about 3-1/16 grains. At one time the carat was not the same weight in
all countries, the international carat is equal to "205 gram., or about
3.164 troy grains. Thus an English ounce troy equals nearly 152 carats.
Originally the carat was considered equal to 4 grains, but when spoken
of now as equalling that amount it means diamond grains, and has no
reference to either troy or avoirdupois weights.
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