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The spinel structure is also interesting because it may contain vacancies as regular part of the crystal. For example, if magnetite is slowly oxidized by lying around a couple of billion years, or when rocks cool, Fe2+ will turn into Fe3+ (oxidation, in chemical terms, means you take electrons away).
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www.tf.uni-kiel.de/matwis/amat/def_en/kap_2/basics/b2_1...
www.tf.uni-kiel.de/matwis/amat/def_en/kap_2/basics/b2_1_6.html
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CoFe2O4 has an inverse spinel crystal structure. The normal crystal structure of an AB2O4 spinel consists of the A2+ atoms occupying all of the tetrahedral coordination sites and the B3+ atoms occupying all of the octahedral sites[2].
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wikis.lib.ncsu.edu/index.php/Spinel
wikis.lib.ncsu.edu/index.php/Spinel
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Further structural investigations by high-resolution neutron powder diffraction in the temperature range 1.6 K ≤T≤280 K confirmed the spinel structure with an almost complete cation inversion corresponding to an inversion parameter of 0.94. A mutually consistent description of the neutron diffraction data,
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www.iop.org/EJ/abstract/0953-8984/17/23/013
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Mineral Structure and Property Data ... The Spinel group is composed of the ... The crystal structure of spinel.
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ruby.colorado.edu/~smyth/min/spinel.html
ruby.colorado.edu/~smyth/min/spinel.html
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Fracture filling (oiling or opticon) enhancement of emerald and the resulting disputes between gemologists and gem dealers. ... Today, the list of compounds recognized to possess the spinel crystal structure is imposing. Table I (partly reproduced from Grimes24) illustrates the vast variety of spinels.
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www.ruby-sapphire.com/spinel.htm
www.ruby-sapphire.com/spinel.htm
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Brunogeierite, Fe2GeO4, a = 8.4127(7) Å, V = 595.4(1) Å3, is a rare germanate spinel from Tsumeb, Namibia. Its structure has been refined to an R index of 2.2%. The oxygen parameter, u, is 0.2466(1), indicating nearly ideal cubic close-packing of oxygen atoms. ... KEYWORDS: brunogeierite, spinel, crystal structure...
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minmag.geoscienceworld.org/cgi/content/abstract/65/3/44...
minmag.geoscienceworld.org/cgi/content/abstract/65/3/441
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The crystal structure, determined from single-crystal X-ray diffraction data collected at 295 K (tetragonal, space group I ... Apparently, Ca4Fe1.5Al17.67O32 represents a new structure type exhibiting more pronounced structural modifications relative to the spinel aristotype compared with the so-called spinelloid structures.
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ammin.geoscienceworld.org/cgi/content/abstract/86/11-12...
ammin.geoscienceworld.org/cgi/content/abstract/86/11-12/1477
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Spinel single crystals of four compositions along the MgAl2O4–MgMn2O4 join, with Mn3+ up to 0.25 apfu, were synthesized by use of a flux-growth method. The crystals were analyzed by electron microprobe, X-ray single-crystal diffraction, and optical absorption spectroscopy.
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ammin.geoscienceworld.org/cgi/content/abstract/92/1/27
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Argon Ar Cubic close-packed structure ... Zinc Zn Hexagonal close-packed structure ... Potassium K Body-centered cubic structure...
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www.ratio.co.jp/english/education/cd_crystal/ecd_crysta...
www.ratio.co.jp/english/education/cd_crystal/ecd_crystal_06.html
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