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Grossular is a calcium-aluminium species of the garnet group of . It has the chemical formula of Ca3Al2(SiO4)3 but the calcium may, in part, be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botany 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. Grossular is a gemstone.
In geological literature, grossular has often been called grossularite. Since 1971, however, use of the term grossularite for the mineral has been discouraged by the International Mineralogical Association.
It has a characteristic red color, inclining to orange or yellow, much like that of zircon. It was shown many years ago, by Sir Arthur Herbert Church, that many , especially (commonly regarded as zircon), were actually hessonite. The difference is readily detected by the specific gravity, that of hessonite being 3.64 to 3.69, while that of zircon is about 4.6. Hessonite has a similar hardness to that of quartz (being about 7 on the mohs scale), while the hardness of most garnet species is nearer 7.5.
Hessonite comes chiefly from Sri Lanka and India, where it is found generally in Placer mining deposits, though its occurrence in its native matrix is not unknown. It is also found in Brazil and California.
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. Viluite Mindat database 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.The System of Mineralogy of James Dwight Dana. Descriptive Mineralogy By James Dwight Dana, Edward Salisbury Dana, 1892, p. 479-80 It comes from the Vilyuy River area in Siberia. A similar green grossular garnet can be found in the Wah Wah mountain range in Utah.[2] Mindat database, accessed 15 October 2023
Grossular is known by many other names, and also some ; Grossular Mindat mineral database, accessed January 25, 2007 colophonite – coarse granules of garnet Colophonite The Free Dictionary, accessed online January 25, 2007 (was later identified as a variety of andradite), ernite, gooseberry-garnet – light green colored and translucent, Gooseberry Garnet WordWeb Online olyntholite/ olytholite, romanzovite, and tellemarkite. Misnomers include Grossular The Mineral and Gemstone Kingdom, accessed online January 25, 2007 South African jade, garnet jade, Transvaal jade, and African jade.
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