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The Gemstone Grossular (Garnet)

Grossular is the most varicolored of the Garnets. The term Garnet describes a group name for several closely related minerals that form important gemstones, and Grossular is an individual member mineral of the Garnet group. Pure Grossular is colorless; the wide range of colors in this Garnet is caused by various impurities. Some Grossular types have their own unique variety or trade names, and are only called by these names in the gemstone market. The orange-brown Hessonite and deep green Tsavorite varieties are the best known varieties. In the gem trade, the term Grossularite is synonymous with Grossular, and both names are acceptable names for describing this gemstone.

Color

White, Colorless, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray

Hardness

6.5 - 7.5

Chemical Formula

Ca₃Al₂Si₃O₁₂

Mineral Class

Grossular (Garnet)

Additional Properties

Crystal System
Isometric

Refractive Index
1.738 - 1.745

Double Refraction
None

Transparency
Transparent

SG
3.6

Luster
Vitreous to adamantine

Cleavage None

All About

Of the Grossular Garnets, Hessonite and the yellow to yellow-green form are the varieties most often used as gemstones. The rare green Tsavorite is the most valuable Grossular variety, if not the most valuable Garnet type in general. Tsavorite is a relatively recent gemstone type, and having been marketed well, created a new gemstone sensation and very good substitute for Emerald. The other forms of Garnet, such as the raspberry-red variety from Mexico and rare colorless type, are seldom used as gemstones. In the gem trade, the term Grossular or Grossularite on its own usually describes only the yellowish to yellowish green form of Grossular.

Uses

Grossular Garnet can be cut into various gems, although it is not used as extensively as the other Garnet forms. It is not commonly seen in jewelry, though Hessonite and the yellow-green to yellow variety are increasing in popularity. For additional information on the uses of Tsavorite, see the Tsavorite gemstone page.

A compact, massive form called Hydrogrossular is sometimes used as carving gemstone and polished in cabochons. Hydrogrossular is usually greenish, but can also be pink and multicolored.

Other Names

Grossularite
Wiluite

Varieties

Gooseberry Garnet - Light green to light greenish-brown variety of Grossular Garnet.
Hessonite - Orange to orange-brown, transparent variety of Grossular Garnet.
Hydrogrossular - Massive veins of opaque Grossular Garnet that resembles Jade. It is white to light green in color, and may be colored in a white, green, and pink combination. Hydrogrossular is often regarded as a variety of Grossular, but it is scientifically regarded as two distinct individual mineral species that have a slightly different chemical formula than true Grossular. Hydrogrossular is synonymous with the term Hydrogarnet. Other synonyms of Hydrogrossular include Transvaal Jade, African Jade, South African Jade, and Garnet Jade.
See the mineral page on Hydrogarnet for more information.
Imperial Garnet - Light pink, transparent gem variety of Grossular Garnet.
Leuco-garnet - Colorless, transparent variety of Grossular Garnet.
Mali Garnet - Garnet gemstone from the African country of Mali that ranges in color from green to yellow to brown (though most often a greenish-yellow). The deposit of these Garnets was discovered in Mali in 1994, and this form of Garnet is a relatively new gemstone. The scientific classification of the Mali Garnets are not clearly identified; they can be either Grossular or Andradite, though are usually an intermediary form closer in chemical structure to Grossular.
Mint Garnet - Grossular Garnet with a light-mint-green color.
Raspberry Garnet - Raspberry-red variety of Grossular Garnet.
Rosolite - Light pink to raspberry-red variety of Grossular Garnet.
Tsavorite - Green to emerald-green transparent variety of Grossular Garnet from Africa.

Treatments & Enhancements

Grossular gemstones are not enhanced, and their colors are always natural.

The Gemstone Grossular (Garnet) Sources

Sources of Grossular Garnet include Kenya, Tanzania, Mali, Italy, Russia, Mexico, Canada (Quebec), and the U.S. (Maine, Vermont, and California).

Similar Gemstones

There are many gemstones that can resemble Grossular gemstones. Topaz and Citrine can be very similar to Hessonite, and yellow Topaz, Heliodor, and Peridot can look similar to yellow to yellowish-green Grossular. Emerald and green Tourmaline can have the same color as the Tsavorite variety.