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PRECIOUS STONES 47
mon.
They are frequently muddy, especially those of the finer shades of
color. White, glistening streaks in the grain of the stone, called
silk, are of frequent occurrence. As a rule, these can be seen at one
angle only; sometimes from the back alone. If silk shows plainly when
the stone is faced up, it is one of the most serious defects.
Sapphires
are subject to the same peculiarities. Irregular coloring is even more
common. Many fine stones depend on a small section around the culet for
their exquisite color. For this reason it is dangerous to recut an
irregularly India-cut stone. It will generally be found, if the culet
is off from the centre, that it was cut there to catch a fine piece of
color. Close examination will show that many sapphires are made up of
sections of white and blue, and in some cases a streak of red will be
found.
Emeralds
are invariably imperfect. The worst imperfections are those which give
the stone a muddy appearance, and others which break the color by
reflecting light, glistening spots and streaks in the body of the
stone. Ordinary grain-marks, red spots, etc., which do not appear to
the naked eye, must be expected.
An
even distribution of color is very desirable, and is best obtained in
step-cut stones by cutting them rather thick. Thin stones do not centre
well for color or brilliancy, the table showing up flat and dark, with
the color confined to the edge facets.
The
fire and glitter of the diamond cannot be expected in colored stones,
but a great degree of brilliancy is often found in those which are now
being cut diamond fashion, as the zircon, white and colored topaz,
amethyst, beryl, etc., as well as the more precious corundums and
emerald.
To
summarize, the qualifications to be desired in this class of jewels,
are color, brilliancy, even distribution of color, perfection, and cut.
All these are rarely found combined, and the dealer must be prepared
to sacrifice desire in
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