The
gemstone is the various minerals that are highly prized for beauty, durability,
and rarity. The organic origin (e.g., pearl, red coral, and amber) noncrystalline materials are also are
classified as gemstones.
From ancient times Gemstones have attracted
humankind, and it also has been used for jewelry. The beauty of the gemstone
may be in colour or in without colour its extreme limpidity and fire provide
the attraction. Iridescence, opalescence, asterism (the exhibition of a
star-shaped figure in reflected light), chatoyance (the exhibition of a
changeable luster and a narrow, undulating band of white light), pattern, and
luster are other features that may make a gemstone beautiful.
The
gemstone is also used as jewelry. By
many civilizations, it was regarded as miraculous and endowed with mysterious
powers. Stones were graced with different and sometimes attributes overlapping;
the diamond, for instance, was thought to give its wearer strength in battle
and to protect him against ghosts and magic. In modern practice, vestiges of
such beliefs persist in wearing a birthstone.
We cut and polished the Gemstones in any of
three ways. The stones are irregular in
shape and become polished. Second, the same kinds of gemstones may instead be
cut en cabochon (i.e., with a rounded upper surface and a flat underside) and
polished on the water- or motor-driven sandstone wheels. To grind facets we used another tool i.e the
dental engine, which has greater flexibility and sensitiveness than the
lathe. Using these facets tools are
ground onto the stone and then are polished as described above.
In
the modern treatment of gemstones of decisive significance was the kind of
cutting known as faceting, which produces brilliance by the refraction and
reflection of light. Gems of all kinds were simply cut either en cabochon or,
especially for purposes of incrustation, into flat platelets until the late
Middle Ages.
To
improve the appearance of stones by covering natural flaws it is necessary to
cutting and faceting it. The detailed knowledge of the crystal structure of
stone, depends on a proper cutting, however.
that the abrasive property of diamond was discovered and used (nothing
else will cut diamond) moreover, it was only in the 15th century. After the
discovery of gemstone, the art of cutting and polishing diamonds and other gems
was developed, probably in France and the Netherlands first. In the 17th century the rose cut was developed,
and the brilliant cut, now the general favourite for diamonds, is said to have
been used for the first time about 1700.
The cabochon method continues to be used for
opaque, translucent, and some transparent stones, such as opal, carbuncle, and
so on in modern gem cutting.
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