transparent to translucent yellow, may show chatoyancy
Andradite includes three varieties:
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.[6]
Demantoid: Vivid green in color, one of the most valuable and rare stones in the gemological world.[7]
Topazolite: Yellow-green in color and sometimes of high enough quality to be cut into a faceted gemstone, it is rarer than demantoid.[7]
^ abcdGrande, Lance; Augustyn, Allison (2009). Gems and Gemstones: Timeless Natural Beauty of the Mineral World. University of Chicago Press. pp. 188–91. ISBN978-0-226-30511-0.
^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. ISBN1-59942-316-2.
^Enver Murad (1984): "Magnetic ordering in andradite." American Mineralogist 69, no. 7-8; pp. 722–24.
External linksedit
Media related to Andradite at Wikimedia Commons
January 01, 1970
andradite, mineral, species, garnet, group, nesosilicate, with, formula, ca3fe2si3o12, single, crystal, diakon, nioro, sahel, circle, kayes, region, maligeneralcategorygarnet, groupformula, repeating, unit, ca3fe2, sio4, 3ima, symboladr, strunz, classification. Andradite is a mineral species of the garnet group It is a nesosilicate with formula Ca3Fe2Si3O12 Andradite Adr Single crystal 4 2 cm Diakon Nioro du Sahel Circle Kayes Region MaliGeneralCategoryGarnet groupFormula repeating unit Ca3Fe2 SiO4 3IMA symbolAdr 1 Strunz classification9 AD 25Crystal systemCubicCrystal classHexoctahedral m3 m H M symbol 4 m 3 2 m Space groupIa3 dUnit cella 12 056 A Z 8IdentificationColorYellow greenish yellow to emerald green dark green brown brownish red brownish yellow grayish black black may be sectoredCrystal habitCommonly well crystallized dodecahedra trapezohedra or combinations also granular to massiveCleavagenoneFractureconchoidal to unevenTenacityBrittleMohs scale hardness6 5 to 7LusterAdamantine to resinous dullStreakWhiteDiaphaneityTransparent to translucentSpecific gravity3 859 calculated 3 8 3 9 measuredOptical propertiesIsotropic typically weakly anisotropicRefractive indexn 1 887Absorption spectrademantoid 440 nm band or complete absorption at 440 nm and below may also have lines at 618 634 685 690 nm 2 References 2 3 4 5 Major varietiesDemantoidtransparent light to dark green to yellow greenMelaniteopaque blackTopazolitetransparent to translucent yellow may show chatoyancy Andradite includes three varieties 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 6 Demantoid Vivid green in color one of the most valuable and rare stones in the gemological world 7 Topazolite Yellow green in color and sometimes of high enough quality to be cut into a faceted gemstone it is rarer than demantoid 7 It was first described in 1868 for an occurrence in Drammen Buskerud Norway 3 4 7 Andradite was named after the Brazilian statesman naturalist professor and poet Jose Bonifacio de Andrada e Silva 1763 1838 3 7 Contents 1 Occurrence 2 See also 3 References 4 External linksOccurrence editIt 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 3 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 Ia3 d with unit cell parameter of 12 051 A at 100 K 8 The spin structure of andradite contains two mutually canted equivalent antiferromagnetic sublattices 9 below the Neel temperature TN 11 K 10 nbsp Black crystals of andradite melaniteSee also editAlmandine Geology Grossular Mineral Mineral collecting Pyrope Spessartine Tsavorite UvaroviteReferences edit Warr L N 2021 IMA CNMNC approved mineral symbols Mineralogical Magazine 85 3 291 320 Bibcode 2021MinM 85 291W doi 10 1180 mgm 2021 43 S2CID 235729616 a b Gemological Institute of America GIA Gem Reference Guide 1995 ISBN 0 87311 019 6 a b c d Handbook of Mineralogy a b Andradite Mindat org Webmineral data Melanite Mindat org a b c d Grande Lance Augustyn Allison 2009 Gems and Gemstones Timeless Natural Beauty of the Mineral World University of Chicago Press pp 188 91 ISBN 978 0 226 30511 0 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 External links edit nbsp Media related to Andradite at Wikimedia Commons Retrieved from https en wikipedia org w index php title Andradite amp oldid 1195276284, wikipedia, wiki, book, books, library,
