What are gemstones?
 The precious materials most widely used in jewelry are gems
– any precious or semiprecious stone. By definition
this group also includes some animal and vegetable
products with precious characteristics, such as amber,
pearls, and coral.
Gemstones have attracted humankind since ancient times, and have long
been used for jewelry. The prime requisite for a gem is
that it must be beautiful. The beauty may lie in colour
or lack of colour; in the latter case, extreme limpidity
and "fire" may provide the attraction.
A gem must
also be durable, if the stone is to retain the polish
applied to it and withstand the wear and tear of
constant handling.
In addition to
their use as jewelry, gems were regarded by many
civilizations as miraculous and endowed with mysterious
powers. Different stones were endowed with different and
sometimes overlapping attributes; the diamond, for
instance, was thought to give its wearer strength in
battle and to protect him against ghosts and magic.
Vestiges of such beliefs persist in the modern practice
of wearing a birthstone.
The physical
properties of gemstones, their hardness, their specific
gravity or density and they way they break, depend on
chemical bonding and the atomic structure within the
stone.
Inclusions are
internal features of gems. The may be solids, liquids,
or gases that the crystal enclosed as it grew, or
cleavages, cracks, and fractures that filled after the
host material finished growing.
The most usual
method of fashioning a gem is to cut the surface into a
number of flat faces, known as facets. This gives the
stone its final shape and "cut"
Finally, color
is the most important factor in determining the value of
gemstones and its the most obvious visual feature, but
in fact it is just one of many optical properties, all
of which are dependent upon light. |
