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Orthorhombic polymorph of rengeite from Ohmi region, central Japan

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Published/Copyright: April 1, 2015
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American Mineralogist
From the journal American Mineralogist Volume 93 Issue 7

Abstract

Rengeite, Sr4ZrTi4(Si2O7)2O8, is a Sr-analog mineral of perrierite and occurs as an accessory mineral in natrolite, pectolite, and itoigawaite veins associated with jadeitic rock from Ohmi-Itoigawa region, Japan. The symmetry of this mineral is reported to be monoclinic. Here, we found an orthorhombic polymorph of rengeite that occurs as micro domains up to 5 pm in width in monoclinic rengeite crystals using electron diffraction and high-resolution TEM analyses. X-ray diffraction analysis us­ing a Gandolfi camera also revealed the presence of the orthorhombic phase in monoclinic rengeite crystals. The unit-cell dimensions of the orthorhombic polymorph are a = 14.0, b = 5.7, c = 21.9 Å, V= 1748 Å3, and Z = 4. Although the space group of orthorhombic polymorph of rengeite has not been determined, the possible space group is Pbca or a similar one from theoretical consideration by Ito (1950). The chemical composition was determined by ATEM-EDS analysis to be SiO2 = 22.5, TiO2 = 30.2, SrO = 39.4, Nb2O5 = 0.2, Fe2O3 = 0.3, and ZrO2 = 7.5, totaling 100.1 wt%, and the ideal chemical formula is Sr4ZrTi4(Si2O7)2O8. Detailed HRTEM imaging revealed that the unit cell of the orthorhombic polymorph of rengeite can be interpreted as a superstructure of monoclinic rengeite, accompanied by repeated twinning on (001) plane. The HRTEM images taken were consistent with the simulated images

Keywords: Rengeite; perrierite; polymorph; jadeite; HRTEM
Received: 2007-4-26
Accepted: 2008-1-26
Published Online: 2015-4-1
Published in Print: 2008-7-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. Rietveld structure refinement of MgGeO3 post-perovskite phase to 1 Mbar
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  6. The structure of monohydrocalcite and the phase composition of the beachrock deposits of Lake Butler and Lake Fellmongery, South Australia
  7. First-principles calculation of the infrared spectrum of hematite
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  19. Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD
  20. Origin of titanite in metarodingite from the Zagros Thrust Zone, Iraq
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  24. New insights into the crystal chemistry of epididymite and eudidymite from Malosa, Malawi: A single-crystal neutron diffraction study
  25. Mechanisms of rhyolitic glass hydration below the glass transition
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https://doi.org/10.2138/am.2008.2689
Keywords for this article
Rengeite; perrierite; polymorph; jadeite; HRTEM

Articles in the same Issue

  1. Rietveld structure refinement of MgGeO3 post-perovskite phase to 1 Mbar
  2. High-temperature ammonium white mica from the Betic Cordillera (Spain)
  3. Synthesis and crystal structure of the feldspathoid CsAlSiO4: An open-framework silicate and potential nuclear waste disposal phase
  4. The crystal chemistry of Li in gadolinite
  5. The effect of the hedenbergitic substitution on the compressibility of jadeite
  6. The structure of monohydrocalcite and the phase composition of the beachrock deposits of Lake Butler and Lake Fellmongery, South Australia
  7. First-principles calculation of the infrared spectrum of hematite
  8. In situ observations of muscovite dissolution under alkaline conditions at 25–50 °C by AFM with an air/fluid heater system
  9. Ramanite-(Cs) and ramanite-(Rb): New cesium and rubidium pentaborate tetrahydrate minerals identified with Raman spectroscopy
  10. Pressure-temperature studies of talc plus water using X-ray diffraction
  11. Hematite and magnetite precipitates in olivine from the Sulu peridotite: A result of dehydrogenation-oxidation reaction of mantle olivine?
  12. Arsenide in a metasomatized peridotite xenolith as a constraint on arsenic behavior in the mantle wedge
  13. Multiple oxygen sites in synthetic phyllosilicates with expandable layers: 17O solid-state NMR study
  14. On the existence of a Na-deficient monoclinic trinepheline with composition Na7.85Al7.85Si8.15O32
  15. Chlorite and biotite weathering, Fe2+-rich corrensite formation, and Fe behavior under low Po₂ conditions and their implication for Precambrian weathering
  16. Structural characterization of natural UO2 at pressures up to 82 GPa and temperatures up to 2200 K
  17. Dense hydrous magnesium silicates, phase D, and superhydrous B: New structural constraints from one- and two-dimensional 29Si and 1H NMR
  18. Mid-IR bands of synthetic calcic amphiboles of tremolite-pargasite series and of natural calcic amphiboles
  19. Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD
  20. Origin of titanite in metarodingite from the Zagros Thrust Zone, Iraq
  21. Experimental calibration of aluminum partitioning between olivine and spinel as a geothermometer
  22. Single-crystal X-ray diffraction study of CaIrO3
  23. Orthorhombic polymorph of rengeite from Ohmi region, central Japan
  24. New insights into the crystal chemistry of epididymite and eudidymite from Malosa, Malawi: A single-crystal neutron diffraction study
  25. Mechanisms of rhyolitic glass hydration below the glass transition
  26. Heat capacity and entropy of melanophlogite: Molecule-containing porosils in nature
  27. Crystal structure of glaucodot, (Co,Fe)AsS, and its relationships to marcasite and arsenopyrite
  28. Modification of gas speciation in quartz-hosted fluid inclusions by stray laser radiation during LA-ICPMS analysis
  29. A PH₂O-dependent structural phase transition in the zeolite natrolite
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