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Crystal structures of synthetic melanotekite (Pb2Fe2Si2O9), kentrolite (Pb2Mn2Si2O9), and the aluminum analogue (Pb2Al2Si2O9)

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Published/Copyright: April 1, 2015
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American Mineralogist
From the journal American Mineralogist Volume 93 Issue 4

Abstract

Synthetic crystals of melanotekite and kentrolite were obtained at 850 °C from melt. The aluminum analogue of kentrolite Pb2Al2Si2O9 was hydrothermally synthesized at 2 GPa, 650 °C together with zoisite-(Pb) and margarite-(Pb). Synthesis products were characterized by single-crystal diffraction studies and microprobe analysis.

The aluminum analogue Pb2Al2Si2O9 was observed in space group Pbcn with lattice parameters a = 6.8981(7) Å, b = 10.6906(15) Å, c = 9.7413(10) Å, and V = 718.37 Å3. Fourier mappings show no irregularities of the Pb site.

Melanotekite with lattice parameters a = 6.9786(6) Å, b = 11.0170(11) Å, c = 10.0895(9) Å, and V = 775.71(17) Å3 in space group Pbcn show a slightly deformed Pb-position in Fourier mappings.

Kentrolite was observed in space group P21221 with pseudo-symmetry to Pbcn with lattice parameters a = 7.0103(5) Å, b = 11.0729 (7) Å, c = 9.9642(7) Å, and V = 773.47(11) Å3. Fourier mappings of the kentrolite structure show that two different split Pb sites exist, which causes lower symmetry. The unit-cell volume of different members of the kentrolite group is a linear function of trivalent ionic radii in sixfold coordination for the elements Al, Ga, In, and also for Fe and Mn in high spin mode.

The structure of Pb2M2Si2O9 (M = Al3+, Fe3+, Mn3+) is built on isolated M-octahedra chains parallel c, M-octahedra sharing alternately trans and skew edges. Each Si2O7-group is linked with their vertices to three octahedra chains. Their Si-O-Si bond angles depend on the size of M-octahedra and are 129.84° in Pb2Al2Si2O9, 131.08° in Pb2Fe2Si2O9, 128.34° and 130.33° in Pb2Mn2Si2O9.

Keywords: Kentrolite; melanotekite; Pb2Al2Si2O9; Pb2Fe2Si2O9; Pb2Mn2Si2O9; crystal-structure; X-ray-diffraction; EMP-analysis
Received: 2007-2-4
Accepted: 2007-11-12
Published Online: 2015-4-1
Published in Print: 2008-4-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Compositional variability and crystal structural features of guanacoite
  2. Interferometric study of pyrite surface reactivity in acidic conditions
  3. White mica domain formation: A model for paragonite, margarite, and muscovite formation during prograde metamorphism
  4. High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation
  5. Time-resolved synchrotron powder X-ray diffraction study of magnetite formation by the Fe(III)-reducing bacterium Geobacter sulfurreducens
  6. Low-temperature calorimetric and magnetic data for natural end-members of the axinite group
  7. Temperature derivatives of elastic wave velocities in plagioclase (An51±1) above and below the order-disorder transition temperature
  8. Disordered silica with tridymite-like structure in the Twiggs clay
  9. Crystal structures of synthetic melanotekite (Pb2Fe2Si2O9), kentrolite (Pb2Mn2Si2O9), and the aluminum analogue (Pb2Al2Si2O9)
  10. Structure and reactivity of synthetic Co-substituted goethites
  11. The crystal chemistry of Fe-bearing sphalerites: An infrared spectroscopic study
  12. Effects of hydration on the structure and compressibility of wadsleyite, β-(Mg2SiO4)
  13. Metastability of sillimanite relative to corundum and quartz in the kyanite stability field: Competition between stable and metastable reactions
  14. Diffusion, discontinuous precipitation, metamorphism, and metasomatism: The complex history of South African upper-mantle symplectites
  15. Thermal behavior of a Ti-rich phlogopite from Mt. Vulture (Potenza, Italy): An in situ X-ray single-crystal diffraction study
  16. The high-pressure behavior of an Al- and Fe-rich natural orthopyroxene
  17. High-pressure phase relation of MnSiO3 up to 85 GPa: Existence of MnSiO3 perovskite
  18. Linking Mössbauer and structural parameters in elbaite-schorl-dravite tourmalines
  19. Synchrotron powder X-ray diffraction study of the structure and dehydration behavior of palygorskite
  20. Maskelynite-hosted apatite in the Chassigny meteorite: Insights into late-stage magmatic volatile evolution in martian magmas
  21. Eskolaite associated with diamond from the Udachnaya kimberlite pipe, Yakutia, Russia
  22. Lakebogaite, CaNaFe23+H(UO2)2(PO4)4(OH)2(H2O)8, a new uranyl phosphate with a unique crystal structure from Victoria, Australia
  23. Letter. Crystal structure and Raman spectrum of hydroxyl-bästnasite-(Ce), CeCO3(OH)
https://doi.org/10.2138/am.2008.2594
Keywords for this article
Kentrolite; melanotekite; Pb2Al2Si2O9; Pb2Fe2Si2O9; Pb2Mn2Si2O9; crystal-structure; X-ray-diffraction; EMP-analysis

Articles in the same Issue

  1. Compositional variability and crystal structural features of guanacoite
  2. Interferometric study of pyrite surface reactivity in acidic conditions
  3. White mica domain formation: A model for paragonite, margarite, and muscovite formation during prograde metamorphism
  4. High-pressure phase transitions in MgSiO3 orthoenstatite studied by atomistic computer simulation
  5. Time-resolved synchrotron powder X-ray diffraction study of magnetite formation by the Fe(III)-reducing bacterium Geobacter sulfurreducens
  6. Low-temperature calorimetric and magnetic data for natural end-members of the axinite group
  7. Temperature derivatives of elastic wave velocities in plagioclase (An51±1) above and below the order-disorder transition temperature
  8. Disordered silica with tridymite-like structure in the Twiggs clay
  9. Crystal structures of synthetic melanotekite (Pb2Fe2Si2O9), kentrolite (Pb2Mn2Si2O9), and the aluminum analogue (Pb2Al2Si2O9)
  10. Structure and reactivity of synthetic Co-substituted goethites
  11. The crystal chemistry of Fe-bearing sphalerites: An infrared spectroscopic study
  12. Effects of hydration on the structure and compressibility of wadsleyite, β-(Mg2SiO4)
  13. Metastability of sillimanite relative to corundum and quartz in the kyanite stability field: Competition between stable and metastable reactions
  14. Diffusion, discontinuous precipitation, metamorphism, and metasomatism: The complex history of South African upper-mantle symplectites
  15. Thermal behavior of a Ti-rich phlogopite from Mt. Vulture (Potenza, Italy): An in situ X-ray single-crystal diffraction study
  16. The high-pressure behavior of an Al- and Fe-rich natural orthopyroxene
  17. High-pressure phase relation of MnSiO3 up to 85 GPa: Existence of MnSiO3 perovskite
  18. Linking Mössbauer and structural parameters in elbaite-schorl-dravite tourmalines
  19. Synchrotron powder X-ray diffraction study of the structure and dehydration behavior of palygorskite
  20. Maskelynite-hosted apatite in the Chassigny meteorite: Insights into late-stage magmatic volatile evolution in martian magmas
  21. Eskolaite associated with diamond from the Udachnaya kimberlite pipe, Yakutia, Russia
  22. Lakebogaite, CaNaFe23+H(UO2)2(PO4)4(OH)2(H2O)8, a new uranyl phosphate with a unique crystal structure from Victoria, Australia
  23. Letter. Crystal structure and Raman spectrum of hydroxyl-bästnasite-(Ce), CeCO3(OH)
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