Hydrogrossular 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 t ...

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. I ...

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 s ...

series (formula: Ca₃Al₂(SiO₄)_3−''x''(OH)_4''x'', with hydroxide (OH) partially replacing silica (SiO₄)). The endmembers of the hydrogarnet family (

grossular Grossular is a calcium-aluminium species of the garnet group of minerals. 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 t ...

, hibschite, and katoite) depend on the degree of substitution (''x''): * grossular: ''x'' = 0 * hibschite: 0.2 < ''x'' < 1.5 * katoite: 1.5 < ''x'' < 3. Hydrogrossular is a garnet variety in which a Si⁴⁺ is missing from a tetrahedral site. Charge balance is maintained by bonding a H⁺ to each of the four oxygens surrounding the vacant site. Hydrogrossular is found in massive crystal habit, sometimes grown in with

idocrase Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as Tetragonal crystal system, tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. It w ...

. Hydrogrossular is

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...

opaque Opacity or opaque may refer to: * Impediments to (especially, visible) light: ** Opacities, absorption coefficients ** Opacity (optics), property or degree of blocking the transmission of light * Metaphors derived from literal optics: ** In lingu ...

, and found in green to bluish green, pink, white, and gray. The cause of the green color is chromium, and possibly

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

. Pink hydrogrossular is caused by the presence of

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

. Hydrogrossular may have dark gray to black small inclusions. It has similarities to jade, and has the misnomers ''Transvaal jade'', and ''African jade''. Hydrogrossular is sometimes used as a gemstone, being

cabochon A cabochon (; ) is a gemstone that has been shaped and polished, as opposed to faceted. The resulting form is usually a convex (rounded) obverse with a flat reverse. Cabochon was the default method of preparing gemstones before gemstone cutt ...

cut, or made into

bead A bead is a small, decorative object that is formed in a variety of shapes and sizes of a material such as stone, bone, shell, glass, plastic, wood, or pearl and with a small hole for threading or stringing. Beads range in size from under ...

s. Sources for green and pink hydrogrossular are

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, and the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. White hydrogrossular is sourced from

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

and China.

References

External links

Grossular-Hibschite Series on Mindat
Aluminium minerals Calcium minerals Cement Garnet group Garnet gemstones {{silicate-mineral-stub