Andradite
Lua error in Module:Infobox at line 235: malformed pattern (missing ']').
Andradite is a species of the garnet group. It is a nesosilicate, with formula Ca3Fe2Si3O12.
Andradite includes three varieties:
- Melanite: Black in color, referred to as "titanian andradite".[5]
- Demantoid: Vivid green in color, one of the most valuable and rare stones in the gemological world.[6]
- Topazolite: Yellow-green in color and sometimes of high enough quality to be cut into a faceted gemstone, it is rarer than demantoid.[6]
It was first described in 1868 for an occurrence in Drammen, Buskerud, Norway.[3][2][6] Andradite was named after the Brazilian statesman, naturalist, professor and poet José Bonifácio de Andrade e Silva (1763–1838).[2][6]
Occurrence
It occurs in skarns developed in contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites and in alkalic igneous rocks (typically titaniferous). Associated minerals include vesuvianite, chlorite, epidote, spinel, calcite, dolomite and magnetite.[2] It is found in Italy, the Ural Mountains of Russia, Arizona and California and in Dnipropetrovsk Oblast in Ukraine.
As the other garnets andradite crystallizes in the cubic space group [[Ia3d]], with unit-cell parameter of 12.051 Å at 100 K.[7]
The spin structure of andradite contains two mutually canted equivalent antiferromagnetic sublattices [8] below the Néel temperature (TN=11 K [9]).
See also
- garnet
- almandine
- Demantoid
- grossular
- pyrope
- spessartine
- tsavorite
- uvarovite
- geology
- mineral collecting
- mineral
- gemstone
References
<templatestyles src="Reflist/styles.css" />
Cite error: Invalid <references> tag; parameter "group" is allowed only.
<references />, or <references group="..." />- ↑ 1.0 1.1 Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
- ↑ 2.0 2.1 2.2 2.3 Handbook of Mineralogy
- ↑ 3.0 3.1 Andradite, Mindat.org
- ↑ Webmineral data
- ↑ Melanite, Mindat.org
- ↑ 6.0 6.1 6.2 6.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Thomas Armbruster and Charles A. Geiger (1993): "Andradite crystal chemistry, dynamic X-site disorder and structural strain in silicate garnets." European Journal of Mineralogy v. 5, no. 1, p. 59-71.
- ↑ Danylo Zherebetskyy (2010). Quantum mechanical first principles calculations of the electronic and magnetic structure of Fe-bearing rock-forming silicates, PhD Thesis, Universal Publishers/Dissertation.com, Boca Raton, Florida, USA, p. 136. ISBN 1-59942-316-2.
- ↑ Enver Murad (1984): "Magnetic ordering in andradite." American Mineralogist 69, no. 7-8; pp. 722-24.
