The precious materials most widely used in jewellery 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 jewellery.

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.
In addition to their use as jewelry, gems were regarded by many civilizations as miraculous and endowed with mysterious powers.