Emerald is the green variety of the mineral beryl. Other gemstone color varieties that belong to beryl include aquamarine, morganite, and heliodor. Other colors of beryl are simply refered to by their color, such as red beryl.

The wonderful green color of emerald is unparalleled in the gem kingdom. Emerald's precious green color is caused by small amounts of chromium and enhanced by traces of iron. Unlike other beryls, emeralds often contain inclusions and other flaws. These flaws are not looked on as negative aspects for emerald like they would be for other gemstones. Indeed, these flaws are considered part of the character of the stone and are used to assure the purchaser of a natural stone.