The garnet family is large and varied, with members ranging from the common red almandite to the rare green tsavorite and demantoid. The garnets are differently colored minerals all with a common crystal structure and varying (but related) chemical compositions.
Six common varieties of garnet are recognized based on their chemical composition. They are pyrope, almandine, spessartite, grossularite, uvarovite and andradite. There are also some mixed members, such as rhodolite garnet, which is a mixture of pyrope and almandite by composition.
Grossularite (or grossular) garnet is a calcium-aluminum garnet. The name grossular is derived from the botanical name for the gooseberry, grossularia. The grossular group includes the light to medium green grossularite; the cinnamon-colored hessonite; the colorless leuco garnet; a dense opaque green garnet called hydrogrossular; and the rare and valuable deep green tsavorite garnet, colored by chromium.
Grossularite garnet ranges in color from lemon yellow to greenish yellow to yellowish-green and even a mint green.
Grossularite garnet has a high refractive index (1.734-1.759) and thus excellent brilliance. It also has good dispersion or fire, exhibited best by the lighter colored specimens. Grossularite varies in hardness from 6.5 to 7.5 on the Mohs hardness scale. The best specimens of grossularite can easily be confused with the more expensive demantoid garnet. Garnet's good hardness combined with its absence of cleavage make it a very durable stone, suitable for all kinds of jewelry.
Deposits of grossularite are found in a number of locations, including Quebec in Canada; Vermont in the USA; Tanzania, South Africa, Kenya and Mali in Africa; as well as in Russia, Pakistan and Sri Lanka. Most of the green grossularite we have seen recently comes from Kenya, while the hessonite comes from Madagascar. Tsavorite garnet is still found in only one geographic location in the world, in the border area of Kenya and Tanzania.
- First Published: August-27-2008
- Last Updated: February-26-2011
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