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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
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1945-3027
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Volume 97, Issue 10

Issues

A multi-domain gem-grade Brazilian apatite

Tom Baikie
  • Corresponding author
  • School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 Singapore
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/ Martin K. Schreyer / Chui Ling Wong
  • School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 Singapore
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/ Stevin S. Pramana
  • School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 Singapore
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/ Wim T. Klooster
  • The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
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/ Cristiano Ferraris
  • Laboratoire de Minéralogie, USM 201, Muséum National d’Histoire Naturelle, CP 52, 61 Rue Buffon, 75005 Paris, France
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/ Garry J. McIntyre
  • The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
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/ T.J. White
  • Centre of Advanced Microscopy, The Australian National University, Canberra ACT 0200, Australia
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Published Online: 2015-04-02 | DOI: https://doi.org/10.2138/am.2012.4069

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 singlecrystal 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.

Keywords : Apatite; X-ray diffraction; Laue neutron diffraction; synchrotron X-ray diffraction

About the article

Received: 2011-12-01

Accepted: 2012-05-30

Published Online: 2015-04-02

Published in Print: 2012-10-01


Citation Information: American Mineralogist, Volume 97, Issue 10, Pages 1574–1581, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2012.4069.

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© 2015 by Walter de Gruyter Berlin/Boston.Get Permission

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