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FROM THE DEPTHS
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of importance in the stone you wear: The harder it is the surer you are
of durability, polish, and brilliance. Which is why the diamond is the
most valuable of all gems, and not because it is the rarest, as is
popularly supposed.
Aside
from the hardness of a diamond a significant thing is its specific
gravity or weight. You can tell the difference between a real diamond
and a phony by comparing their weight—the heavier one is the real
thing. The specific gravity of a diamond is 3-1/2, meaning a cubic
inch of diamond weighs three and a half times as much as a cubic inch
of pure water.
Diamonds
are measured by a unit—an almost infinitesimal unit—called a carat.
There are 2268 metric carats in a pound, 142 to an ounce, which brings
up the question of what a carat is and how it came to be so named. Many
years ago the systems of weights in various parts of the world were
based upon the seeds of some plant, common in the particular region and
nearly uniform in size and weight. In Europe it was the barley grain.
In the Mediterranean countries it was the locust tree, Ceratonia
siliqua, referring to the hornlike shape of the fruit pods (locust bean
or St. John's bread) of the carob or locust tree. The seeds of this
tree proved remarkably constant in weight, those taken from the ends of
the pulpy pods being no smaller than those from the middle. In England,
for a long time (locust trees don't grow in England), weights were
based on Grayne (grain, such as corn or wheat). In fact, the system of
various weights in England today is a little confused, dealing as it
does with "grains troy" and "grains avoirdupois," which really mean the
same thing. Every country in Europe had a different system, it seemed.
But in the latter part of the nineteenth century a definite standard
was considered and in 1871 the Chambre Syndicate de
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