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 color or lack of color; 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
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.