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Tetrahedral vacancies and cation ordering in low-temperature Mn-bearing vesuvianites: Indication of a hydrogarnet-like substitution

  • Thomas Armbruster EMAIL logo and Edwin Gnos
Published/Copyright: March 26, 2015
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American Mineralogist
From the journal American Mineralogist Volume 85 Issue 3-4

Abstract

Strongly zoned Mn-rich vesuvianites with MnO concentrations up to 14.3 wt% from the N’chwaning II mine of the Kalahari manganese field (South Africa) crystallized at hydrothermal conditions below 450 °C. These vesuvianites are by far the most Mn-rich samples hitherto described and have either space group P4nc or P4/n due to partial long-range ordering. Most crystals are assembled of P4nc and P4/n domains yielding P4 average symmetry. The crystal structure of one Mn-rich crystal of average composition Ca19Mn3.5Al9.5Si17.4(O,OH)78 was refined from single-crystal X-ray data (R1 = 3.85%) in space group P4/n (a = 15.571(2), c = 11.789(2) Å). Mn2+ and Mn3+ are concentrated on the fivefold-coordinated square pyramidal Y′ site. Additional Mn3+ was located on the octahedral sites Y2a (35%), Y1a (22%), Y2b (13%) and Y1b (8%). Electron microprobe analyses and crystal-structure refinements indicated tetrahedral vacancies in the orthosilicate tetrahedra (Z1 and Z2) but not in the disilicate units (Z3). Z1 tetrahedra with up to 17% vacancies have strongly increased Z1-O distances of 1.67 Å. Structural and chemical evidence combined with the similarity of the structures of vesuvianite and garnet suggest a partial hydrogarnet-like substitution of SiO4 tetrahedra by H4O4.

Received: 1999-6-8
Accepted: 1999-10-20
Published Online: 2015-3-26
Published in Print: 2000-4-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Iron concentration and the physical processes of dynamic oxidation in an alkaline earth aluminosilicate glass
  2. A crystal chemical re-evaluation of amphibole/melt and amphibole/clinopyroxene DTi values in petrogenetic studies
  3. Mineralogy of mafic xenoliths and their reaction zones in the olivine lamproite from Prairie Creek Arkansas and the paragenesis of haggertyite, Ba [Fe6Ti5Mg]O19
  4. Magmatic anhydrite in granitic rocks: First occurrence and potential petrologic consequences
  5. Crystal chemistry of Al-rich biotites coexisting with muscovites in peraluminous granites
  6. Spectroscopic and structural properties of synthetic micas on the annite-siderophyllite binary: Synthesis, crystal structure refinement, Mössbauer, and infrared spectroscopy
  7. Thermodynamic properties of tremolite: A correction and some comments
  8. Raman spectroscopic characteristics of Mg-Fe-Ca pyroxenes
  9. Hydrogen in diopside: Diffusion profiles
  10. Diffusion of C and O in calcite at 100 MPa
  11. Solubility and stability of zeolites in aqueous solution: II. Calcic clinoptilolite and mordenite
  12. TEM and SFM of exsolution and twinning in an alkali feldspar
  13. Equation of state of magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure
  14. Optimization of site occupancies in minerals using quadratic programming
  15. Leverage analysis and structure refinement of minerals
  16. The absolute energy positions of conduction and valence bands of selected semiconducting minerals
  17. Antiferroelectric phase transition in titanite: Excess entropy and short range order
  18. P4/n and P4nc long-range ordering in low-temperature vesuvianites
  19. Tetrahedral vacancies and cation ordering in low-temperature Mn-bearing vesuvianites: Indication of a hydrogarnet-like substitution
  20. Sodic-ferripedrizite, a new monoclinic amphibole bridging the magnesium-iron-manganese-lithium and the sodium-calcium groups
  21. The crystal structure of peprossiite-(Ce), an anhydrous REE and Al mica-like borate with square-pyramidal coordination for Al
  22. Crystal chemistry of the new mineral brandholzite, Mg(H2O)6[Sb(OH)6]2, and of the synthetic analogues M2+(H2O)6[Sb(OH)6]2 (M2+ = Mg, Co)
  23. Letters. In-situ Raman spectra of dissolved silica species in aqueous fluids to 900 °C and 14 kbar
  24. Quetzalcoatlite: A new octahedral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal at the Advanced Photon Source-GSE-CARS Facility
  25. Bonding and dynamics of Mg in pyrope: a theoretical investigation
  26. Structure of a new Al-rich phase, [K, Na]0.9[Mg, Fe]2[Mg, Fe, Al, Si]6O12, synthesized at 24 GPa
  27. Core level electron binding energies of realgar (As4S4)
  28. Oxidation of {100} and {111} surfaces of pyrite: Effects of preparation method
https://doi.org/10.2138/am-2000-0419

Articles in the same Issue

  1. Iron concentration and the physical processes of dynamic oxidation in an alkaline earth aluminosilicate glass
  2. A crystal chemical re-evaluation of amphibole/melt and amphibole/clinopyroxene DTi values in petrogenetic studies
  3. Mineralogy of mafic xenoliths and their reaction zones in the olivine lamproite from Prairie Creek Arkansas and the paragenesis of haggertyite, Ba [Fe6Ti5Mg]O19
  4. Magmatic anhydrite in granitic rocks: First occurrence and potential petrologic consequences
  5. Crystal chemistry of Al-rich biotites coexisting with muscovites in peraluminous granites
  6. Spectroscopic and structural properties of synthetic micas on the annite-siderophyllite binary: Synthesis, crystal structure refinement, Mössbauer, and infrared spectroscopy
  7. Thermodynamic properties of tremolite: A correction and some comments
  8. Raman spectroscopic characteristics of Mg-Fe-Ca pyroxenes
  9. Hydrogen in diopside: Diffusion profiles
  10. Diffusion of C and O in calcite at 100 MPa
  11. Solubility and stability of zeolites in aqueous solution: II. Calcic clinoptilolite and mordenite
  12. TEM and SFM of exsolution and twinning in an alkali feldspar
  13. Equation of state of magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure
  14. Optimization of site occupancies in minerals using quadratic programming
  15. Leverage analysis and structure refinement of minerals
  16. The absolute energy positions of conduction and valence bands of selected semiconducting minerals
  17. Antiferroelectric phase transition in titanite: Excess entropy and short range order
  18. P4/n and P4nc long-range ordering in low-temperature vesuvianites
  19. Tetrahedral vacancies and cation ordering in low-temperature Mn-bearing vesuvianites: Indication of a hydrogarnet-like substitution
  20. Sodic-ferripedrizite, a new monoclinic amphibole bridging the magnesium-iron-manganese-lithium and the sodium-calcium groups
  21. The crystal structure of peprossiite-(Ce), an anhydrous REE and Al mica-like borate with square-pyramidal coordination for Al
  22. Crystal chemistry of the new mineral brandholzite, Mg(H2O)6[Sb(OH)6]2, and of the synthetic analogues M2+(H2O)6[Sb(OH)6]2 (M2+ = Mg, Co)
  23. Letters. In-situ Raman spectra of dissolved silica species in aqueous fluids to 900 °C and 14 kbar
  24. Quetzalcoatlite: A new octahedral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal at the Advanced Photon Source-GSE-CARS Facility
  25. Bonding and dynamics of Mg in pyrope: a theoretical investigation
  26. Structure of a new Al-rich phase, [K, Na]0.9[Mg, Fe]2[Mg, Fe, Al, Si]6O12, synthesized at 24 GPa
  27. Core level electron binding energies of realgar (As4S4)
  28. Oxidation of {100} and {111} surfaces of pyrite: Effects of preparation method
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