Grossular

Grossular, also incorrectly called grossularite, is a calcium-aluminium mineral species of the garnet group with the formula Ca₃Al₂(SiO₄)₃,^[1] though the calcium may in part be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow.  

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The more common variety of grossular is called hessonite from the Greek meaning inferior, because of its inferior hardness to zircon, which the yellow crystals resemble. Grossular is found in contact metamorphosed limestones with vesuvianite, diopside, wollastonite and wernerite.

A highly sought after variety of gem garnet is the fine green Grossular garnet from Kenya and Tanzania called tsavorite. This garnet was discovered in the 1960s in the Tsavo area of Kenya, from which the gem takes its name.

Viluite is a variety name of grossular, that is not a recognized mineral species.^[3] It is usually olive green though sometimes brownish or reddish, brought about by impurities in the crystal. Viluite is found associated with and is similar in appearance to vesuvianite, and there is confusion in terminology as viluite has long been used as a synonym for wiluite, a sorosilicate of the vesuvianite group. This confusion in nomenclature dates back to James Dwight Dana.^[4] It comes from the Vilyuy river area in Siberia.

Grossular is known by many other names, and also some misnomers;^[5] colophonite - coarse granules of garnet^[6], ernite, gooseberry-garnet - light green colored and translucent,^[7] kalkthongranat, kanelstein, olyntholite/olytholite, pechgranat, romanzovite, and tellemarkite. Misnomers include;^[2] South African jade, garnet jade, Transvaal jade, and African jade.

References

1. ^ ^{a b c d e f g h i j} Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
2. ^ ^{a b} Grossular The Mineral and Gemstone Kingdom, accessed online January 25, 2007
3. ^ Viluite Mindat database
4. ^ The System of Mineralogy of James Dwight Dana. Descriptive Mineralogy By James Dwight Dana, Edward Salisbury Dana, 1892, p. 479-80
5. ^ Grossular Mindat mineral database, accessed January 25, 2007
6. ^ Colophonite The Free Dictionary, accessed online January 25, 2007
7. ^ Gooseberry Garnet WordWeb Online

• Mineral Galleries grossular data
• Webmineral data
• Mindat grossular data
• Mineral Data Publishing