Garnets are historically one of the most important of the colored gemstones, valued for their good hardness and excellent brilliance. The name garnet actually refers to a family of different gemstones. There are many different varieties of garnet, but no gemstone that is simply called "garnet".
All of the different garnets share a common crystal structure but vary in their chemical composition. Gemology recognizes six common species of garnet based on their different chemical composition. They are pyrope, almandine, spessartite, grossularite, uvarovite and andradite. In addition to these six species, there are a number of other garnet varieties that are distinguished in the gem trade, based on their color or other special properties. Altogether there are at least 17 different varieties of garnet.