From Surf Wiki (app.surf) — the open knowledge base

Andradite

Nesosilicate mineral species of garnet

Field	Value
name	Andradite [Adr]
category	Garnet group
image	Andradite-Mali.jpg
imagesize	260px
caption	Single crystal (4.2cm) – Diakon, Nioro du Sahel Circle, Kayes Region, Mali
formula	Ca3Fe2(SiO4)3
IMAsymbol	Adr
strunz	9.AD.25
system	Cubic
class	Hexoctahedral (mm)
H-M symbol: (4/m 2/m)
symmetry	Iad
unit cell	a = 12.056 Å; Z = 8
color	Yellow, greenish yellow to emerald-green, dark green; brown, brownish red, brownish yellow; grayish black, black; may be sectored
habit	Commonly well-crystallized dodecahedra, trapezohedra, or combinations, also granular to massive
cleavage	none
fracture	conchoidal to uneven
tenacity	Brittle
mohs	6.5 to 7
luster	Adamantine to resinous, dull
diaphaneity	Transparent to translucent
refractive	n = 1.887
opticalprop	Isotropic, typically weakly anisotropic
absorption	demantoid – 440nm band or complete absorption at 440nm and below, may also have lines at 618, 634, 685, 690nm
streak	White
gravity	3.859 calculated; 3.8–3.9 measured
references
var1	Demantoid	var1text = transparent light to dark green to yellow-green
var2	Melanite	var2text = opaque black
var3	Topazolite	var3text = transparent to translucent yellow, may show chatoyancy

H-M symbol: (4/m 2/m)

Andradite garnet - Jiangxi, Nantan, China.

Andradite is a mineral species of the garnet group. It is a nesosilicate, with chemical formula Ca3Fe2Si3O12.

Andradite includes four varieties:

Colophonite: a historical variety found in the Scandinavian islands, brownish or reddish in color, often opaque or translucent.
Demantoid: Vivid green in color, one of the most valuable and rare stones in the gemological world.
Melanite: Black in color due to limited substitution of titanium for iron. Also known as "titanian andradite". Forms a solid solution with morimotoite and schorlomite depending on titanium and iron content.
Topazolite: Yellow-green in color and sometimes of high enough quality to be cut into a faceted gemstone, it is rarer than demantoid.

It was first described in 1868 for an occurrence in Drammen, Buskerud, Norway. Andradite was named after the Brazilian statesman, naturalist, professor and poet José Bonifácio de Andrada e Silva (1763–1838).

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. It is found in Iran, Italy, the Ural Mountains of Russia, Arizona and California and in Dnipropetrovsk Oblast in Ukraine.

Like the other garnets, andradite crystallizes in the cubic space group 3}}d, with unit-cell parameter of 12.051 Å at 100 K.

The spin structure of andradite contains two mutually canted equivalent antiferromagnetic sublattices below the Néel temperature (TN=11 K).

File:Mélanite-Mali.jpg|Black crystals of andradite: melanite

References

Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
Gemological Institute of America, ''GIA Gem Reference Guide'' 1995, {{ISBN. 0-87311-019-6
''[http://rruff.geo.arizona.edu/doclib/hom/andradite.pdf Handbook of Mineralogy]''
[http://www.mindat.org/min-223.html Andradite], Mindat.org
[http://www.webmineral.com/data/Andradite.shtml Webmineral data]
''Olga Bortnik''. All about precious stones. ― Moscow: Harvest, 2011.
(2009). "Gems and Gemstones: Timeless Natural Beauty of the Mineral World". University of Chicago Press.
[http://www.mindat.org/min-7443.html Melanite], Mindat.org
Thomas Armbruster and Charles A. Geiger (1993): "[http://eurjmin.geoscienceworld.org/cgi/content/abstract/5/1/59 Andradite crystal chemistry, dynamic X-site disorder and structural strain in silicate garnets]." ''European Journal of Mineralogy'' v. 5, no. 1, p. 59-71.
Universal Publishers]]/Dissertation.com, Boca Raton, Florida, USA, p. 136. {{ISBN. 1-59942-316-2.
Enver Murad (1984): "[http://ammin.geoscienceworld.org/cgi/content/abstract/69/7-8/722 Magnetic ordering in andradite]." ''American Mineralogist'' 69, no. 7-8; pp. 722–24.

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

calcium-minerals iron(iii)-minerals garnet-gemstones minerals-in-space-group-230 titanium-minerals minerals-described-in-1868

Want to explore this topic further?

Ask Mako anything about Andradite — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report