which are of great lustre, and extremely hard,
as the diamond; the semi-pellucid, those which are not so transparent,
but yet of great beauty; those of one color, as the emerald or
turquois; and those variegated or veined with different colors. Gems
are sometimes found of regular shapes, with a natural polish, near the
beds of rivers after great rains; these are of the pebble kind.
Sometimes they are found of irregular shapes, with a rough coat, in
mines and the clefts of rocks. Pearls, though not stones, are also
ranked among the number of gems.

_Pellucid_, clear as a drop of water.

_Semi-pellucid_, half pellucid.

Describe the Diamond.

The diamond is a precious stone, the first in rank of all the gems,
and valued for its beautiful lustre; it is the hardest of all stones,
as well as the most valuable. The most esteemed are colorless. A
diamond in its natural state as it comes out of the mine, and before
it is cut, is called rough, because it has no brilliancy, but is
covered with an earthy crust. The diamond is the Adamant of the
ancients; hence the expression "hard as adamant," from its being the
hardest substance in nature. The cutting of diamonds is a work of
labor, and requires great skill; the polishing is performed by a mill
of simple construction.

Where are they mostly found?

In yellow ochreous earths; in mines; and likewise in torrents, which
have torn them from their beds. In former times, all the diamonds that
were known were brought from the famous mines of Golconda, in
Hindostan; the islands of Molucca and Borneo have also produced many
valuable stones. The diamond mines of Golconda are now so exhausted,
that they are not thought worth the expense of working; these gems are
now brought chiefly from Brazil, in South America.

What is meant by Ochreous?

Consisting of ochre, a kind of earth with a rough and dusty surface,
composed of fine, soft, clayey particles, which readily separate in
water. There are various colored ochres, as red, yellow, blue, green,
&c.; they are very useful in many of the arts.

What term is used to denote the quality of the Diamond?

In speaking of the value of diamonds, we distinguish them as "diamonds
of the first water," meaning those which possess the greatest
perfection and purity, which ought to be that of the clearest drop of
water: when they fall short of this perfection, they are said to be
"of the second or third water," and so on till t