Garnet is historically one of the most important of the colored gemstones, valued for their good hardness and excellent brilliance. But the name garnet actually refers to a family of different gemstones. There are many different varieties of garnet, but no gemstone which is simply called "garnet."

All of the different garnets share a common crystal structure but they 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 which are distinguished in the gem trade, based on their color or other special properties. All told, there are at least 17 different varieties of garnet.

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

First Published: July-19-2010

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