Grossular is a

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

species of the

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

group of

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s. It has the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

of Ca₃Al₂(SiO₄)₃ but the calcium may, in part, be replaced by ferrous

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and the aluminium by ferric iron. The name grossular is derived from the

botanical Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

name for the

gooseberry Gooseberry ( or (American and northern British) or (southern British)) is a common name for many species of ''Ribes'' (which also includes Ribes, currants), as well as a large number of plants of similar appearance, and also several unrela ...

, ''grossularia'', in reference to the green garnet of this composition that is found in

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

. Other shades include

cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, biscuits, b ...

brown (cinnamon stone variety), red, and yellow. Grossular is a

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

. 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 Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. ...

Hessonite

Hessonite or "cinnamon stone" is a common variety of grossular with the general

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

: Ca₃Al₂Si₃O₁₂. The name comes from the (hēssōn), meaning ''inferior''; an allusion to its lower hardness and lower density than most other garnet species varieties. It has a characteristic red color, inclining to orange or yellow, much like that of

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

. It was shown many years ago, by Sir

Arthur Herbert Church Sir Arthur Herbert Church (2 June 1834 – 31 May 1915) was a British chemist, expert on pottery, stones and chemistry of paintings, who discovered turacin in 1869 and several minerals, including the only British cerium mineral. He was also a tal ...

, that many

s, especially

engraved gem An engraved gem, frequently referred to as an intaglio, is a small and usually semi-precious gemstone that has been carved, in the Western tradition normally with images or inscriptions only on one face. The engraving of gemstones was a major lux ...

s (commonly regarded as zircon), were actually hessonite. The difference is readily detected by the

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

, 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 Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

(being about 7 on the mohs scale), while the hardness of most garnet species is nearer 7.5. Hessonite comes chiefly from

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

and India, where it is found generally in placer deposits, though its occurrence in its native matrix is not unknown. It is also found in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Deposits

Grossular is found in contact metamorphosed

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

s with vesuvianite, diopside,

wollastonite Wollastonite is a calcium Silicate minerals, inosilicate mineral (calcium, Casilicon, Sioxygen, O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or D ...

and

wernerite The scapolites (, "rod", and , "stone") are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite () and marialite (). Silvialite is al ...

. A highly sought after variety of gem garnet is the fine green Grossular garnet from

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

and

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

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. 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 Wiluite is a dark green, brownish, or black blocky silicate mineral with the chemical formula . It has a Mohs hardness of 6 and a specific gravity of 3.36. It has a vitreous lustre, poor cleavage and an irregular brittle fracture. It crystallizes ...

, a sorosilicate of the vesuvianite group. This confusion in nomenclature dates back to

James Dwight Dana James Dwight Dana Royal Society of London, FRS FRSE (February 12, 1813 – April 14, 1895) was an American geologist, mineralogist, volcanologist, and zoologist. He made pioneering studies of mountain-building, volcano, volcanic activity, and the ...

. It comes from the Vilyuy river area in

. A similar green grossular garnet can be found in the Wah Wah mountain range in Utah. Grossular is known by many other names, and also some

misnomer A misnomer is a name that is incorrectly or unsuitably applied. Misnomers often arise because something was named long before its correct nature was known, or because an earlier form of something has been replaced by a later form to which the nam ...

s;Grossular
Mindat mineral database, accessed January 25, 2007 '' colophonite'' – coarse granules of garnet (was later identified as a variety of

andradite Andradite is a Mineralogy, mineral species of the Garnet, garnet group. It is a Silicate minerals#Nesosilicates, nesosilicate, with chemical formula Ca3Fe2Si3O12. Andradite includes three varieties: * ''Colophonite'': a historical variety found ...

), ''ernite'', ''gooseberry-garnet'' – light green colored and translucent, ''olyntholite''/''olytholite'', ''romanzovite'', and ''tellemarkite''. Misnomers includeGrossular
The Mineral and Gemstone Kingdom, accessed online January 25, 2007 ''South African jade'', ''garnet jade'', ''Transvaal jade'', and ''African jade''.

Cultural significance

In 1991,

Vermont Vermont () is a U.S. state, state in the New England region of the Northeastern United States. It borders Massachusetts to the south, New Hampshire to the east, New York (state), New York to the west, and the Provinces and territories of Ca ...

named grossular garnet its state gemstone. File:GrossularShades.jpg, Color range of grossular graphically displayed at the

National Museum of Natural History The National Museum of Natural History (NMNH) is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. With 4.4 ...

Washington, D.C. File:Grossular-195706.jpg, Group of Grossular crystals, largest 1.1 cm, from Val-des-Sources, Quebec

References

External links

Webmineral dataMineral Data Publishing
{{Commons Calcium minerals Aluminium minerals Garnet gemstones

Hessonite

Deposits

Cultural significance

See also

References

External links