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.

Almandine (or Almandite) Garnet Iron aluminum silicate, typically red with a violet tint.
Andradite Garnet Calcium iron silicate, the andradite group includes demantoid, melanite and topazolite.
Color-Change Garnet A mix of spessartite and pyrope garnet. This rare garnet presents a color change from brownish or orange in daylight, to rose-pink in incandescent light.
Demantoid Garnet A type of andradite garnet that is the most valuable of all the garnets, due to its outstanding luster and dispersion.
Grossularite (or Grossular) Garnet Calcium aluminum silicate, the grossular group includes grossularite, hessonite, leuco, hydrogrossular and tsavorite garnet.
Hessonite Garnet A type of grossular garnet that is often called cinnamon stone for its brownish-red color.
Hydrogrossular Garnet A type of grossular green garnet that is dense and opaque, resembling jade.
Leuco Garnet A type of grossular garnet that is entirely colorless.
Mali Garnet One of the hybrid garnets, Mali is a mixture of grossular and andradite garnet. It is green in color with excellent luster and dispersion.
Melanite Garnet An opaque black variety of andradite garnet.
Pyrope Garnet Magnesium aluminum silicate, typically red with a brownish tint.
Rhodolite Garnet One of the hybrid garnets, rhodolite is a mixture of pyrope and almandite garnet. Colors range from ruby-red to purple.
Spessartite (or Spessartine) Garnet Magnesium aluminum silicate, typically mandarin-orange to orange-red.
Star Garnet Garnets that display asterism (the star affect) are rare and have so far been found only in two places in the world (Idaho, USA and India).
Topazolite Garnet A type of andradite garnet that is yellow to lemon-yellow in color. Its similarity to yellow topaz is the reason for its name.
Tsavorite Garnet A type of grossular garnet colored by chrome, resulting in a bright-green to emerald-green color. The second most valuable of all the garnets.
Uvarovite Garnet Calcium chromium silicate, typically emerald-green. It is rarely found in gemstone quality.