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Title: A multi-domain gem-grade Brazilian apatite
Authors: Baikie, Tom
Schreyer, Martin K.
Wong, Chui Ling
Pramana, Stevin S.
Klooster, Wim T.
Ferraris, Cristiano
McIntyre, Garry J.
White, Timothy John
Keywords: Apatite
X-ray diffraction
Laue neutron diffraction
Synchrotron X-ray diffraction
Issue Date: 2012
Source: Baikie, T., Schreyer, M. K., Wong, C. L., Pramana, S. S., Klooster, W. T., Ferraris, C., et al. (2012). A multi-domain gem-grade Brazilian apatite. American Mineralogist, 97(10), 1574-1581.
Series/Report no.: American mineralogist
Abstract: A gem-grade apatite from Brazil of general composition (Ca,Na)10[(P,Si,S)O4]6(F,Cl,OH)2 has been studied using single-crystal X-ray and neutron diffraction together with synchrotron powder X-ray diffraction. Earlier electron microscopy studies had shown the nominally single-phase apatite contains an abundant fluorapatite (F-Ap) host, together with chloro-hydroxylapatites (Cl/OH-Ap) guest phases that encapsulate hydroxylellestadite (OH-El) nanocrystals. While the latter features appear as small (200–400 nm) chemically distinct regions by transmission electron microscopy, and can be identified as separate phases by synchrotron powder X-ray diffraction, these could not be detected by single-crystal X-ray and neutron analysis. The observations using neutron, X-ray and electron probes are however consistent and complementary. After refinement in the space group P63/m the tunnel anions F− are fixed at z = ¼ along <001>, while the anions Cl− and OH− are disordered, with the suggestion that O-H···O-H··· hydrogen-bonded chains form in localized regions, such that no net poling results. The major cations are located in the 4f AFO6 metaprism (Ca+Na), 6h ATO6X tunnel site (Ca only), and 6h BO4 tetrahedron (P+Si+S). The structural intricacy of this gem stone provides further evidence that apatite microstructures display a nano-phase separation that is generally unrecognized, with the implication that such complexity may impact upon the functionality of technological analogues.
ISSN: 0003-004X
DOI: 10.2138/am.2012.4069
Rights: © 2012 Mineralogical Society of America. This is the author created version of a work that has been peer reviewed and accepted for publication by American mineralogist, Mineralogical Society of America. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [].
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MSE Journal Articles

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