Grossular is a

calcium Calcium is a chemical element with the 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 ...

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

species of the

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...

group of

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

s. It has the

chemical formula In chemistry, 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, ...

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

iron Iron () is a chemical element with symbol Fe (from la, ferrum) 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, right in ...

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

botanical Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

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 currants), as well as a large number of plants of similar appearance. The berries of those in the gen ...

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

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...

. 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, breakf ...

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

gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...

. 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. Th ...

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 grc, ἣσσων (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 t ...

. It was shown many years ago, by Sir Arthur Herbert Church, 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, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...

, 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 atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...

(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 (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

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 ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

and

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Deposits

Grossular is found in contact metamorphosed

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

s with

vesuvianite Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. It was first discovered within ...

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...

wollastonite Wollastonite is a calcium inosilicate mineral ( Ca Si O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature ...

and

wernerite The scapolites (Gr. σκάπος, rod, and λίθος, 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 marialit ...

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

Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi , ...

and

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ...

called

tsavorite Tsavorite or tsavolite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca3 Al2 Si3 O12.Gemological Institute of America, ''GIA Gem Reference Guide'' 1995, Trace amounts of vanadium or chromium pro ...

. This garnet was discovered in the 1960s in the

Tsavo Tsavo is a region of Kenya located at the crossing of the Uganda Railway over the Tsavo River, close to where it meets the Athi-Galana-Sabaki River. Two national parks, Tsavo East and Tsavo West are located in the area. The meaning of the w ...

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

, 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 Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually co ...

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

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

. It comes from the

Vilyuy river The Vilyuy ( rus, Вилю́й, p=vʲɪˈlʲʉj; sah, Бүлүү, ''Bülüü'', ) is a river in Russia, the longest tributary of the Lena. About long, it flows mostly within the Sakha Republic. Its basin covers about . History The river is fir ...

area in

. 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 name ...

s;Grossular
Mindat mineral database, accessed January 25, 2007 ''colophonite'' – coarse granules of garnet, ''ernite'', ''gooseberry-garnet'' – light green colored and translucent, ''olyntholite''/''olytholite'', ''romanzovite'', and ''tellemarkite''. Misnomers include
The Mineral and Gemstone Kingdom, accessed online January 25, 2007 ''South African jade'', ''garnet jade'', ''Transvaal jade'', and ''African jade''.

Cultural significance

Vermont Vermont () is a U.S. state, state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York (state), New York to the west, and the Provin ...

has grossular garnet as 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 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. In 2021, with 7. ...

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

Val-des-Sources, Quebec Val-des-Sources (), meaning "Valley of the Springs", formerly known as Asbestos (), is a town in the Estrie (Eastern Townships) region of southeastern Quebec, Canada on the Nicolet River."Asbestos" in '' The New Encyclopædia Britannica''. Ch ...

References

External links

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

Hessonite

Deposits

Cultural significance

See also

References

External links