Gemstone, any of various minerals highly prized for beauty, durability, and rarity. A few noncrystalline materials of organic
origin (e.g., Sapphire, Ruby, and Emerald) also are classified as gemstones.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.
Iridescence, opalescence, aster-ism (the exhibition of a star-shaped figure in reflected light), chatoyance (the exhibition of a
changeable lustre and a narrow, undulating band of white light), pattern, and lustre are other features that may make a gemstone
beautiful. 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.