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The crystal structure of piergorite-(Ce), Ca8Ce2(Al0.5 Fe3+ 0.5)Σ1(□,Li,Be)2Si6B8O36(OH,F)2: A new borosilicate from Vetralla, Italy, with a modified hellandite-type chain

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Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 91 Issue 7

Abstract

Piergorite-(Ce) is a new mineral found at Tre Croci, Vetralla, Italy with simplified formula Ca8Ce2 (Al0.5Fe3+ 0.5)Σ1(□,Li,Be)2Si6B8O36(OH,F)2. It occurs as strong intergrowths of small crystals, colorless to pale yellow, associated with sanidine, mica, magnetite, rutile, titanite, and other Th-U-REE bearing minerals, in miarolitic cavities of a syenitic ejectum. Piergorite-(Ce) is biaxial negative, nα = 1.717 (1), nβ = 1.728 (1), and nγ = 1.735 (1), 2Vmeas = 68(2)°, X = b, and Z ^ c = 7(1)°. Crystals show tabular habit and a very good {010} cleavage; twinning along the (301̄) plane produces “L” forms. The three strongest lines in the simulated powder diffraction pattern (dobs, I, hkl) are: 2.65 Å, 100.0, (213, 4̄13); 1.91 Å, 48.3, (223, 4̄23, 821); 2.90 Å, 44.9, (6̄03, 6̄12). The structure was solved by Patterson synthesis from X-ray diffraction data [monoclinic, space group P2/a, a = 28.097(3) Å, b = 4.777(1) Å, c = 10.236(2) Å, β = 96.81(1)°, V = 1364.2(7) Å3, Z = 2] and was refined to a final Robs = 0.059 for 6480 Fo with Io > 3σ(Io). The structure shows similarities with the hellandite group because Si and B tetrahedra form chains along c. Hellandite structure is characterized by a single chain of five-membered rings, whereas piergorite-(Ce) shows a double chain of five-membered rings interconnected by a single octahedral site to form a three-dimensional framework containing five independent eightfold-coordinated M sites and a partly occupied T-cavity.

Keywords : New mineral; piergorite-(Ce); borosilicate; crystal structure; SIMS; hellandite
Received: 2005-11-8
Accepted: 2006-3-5
Published Online: 2015-3-31
Published in Print: 2006-7-1

© 2015 by Walter de Gruyter Berlin/Boston

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  20. The crystal structure of piergorite-(Ce), Ca8Ce2(Al0.5 Fe3+ 0.5)Σ1(□,Li,Be)2Si6B8O36(OH,F)2: A new borosilicate from Vetralla, Italy, with a modified hellandite-type chain
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https://doi.org/10.2138/am.2006.2139
Keywords for this article
New mineral; piergorite-(Ce); borosilicate; crystal structure; SIMS; hellandite

Articles in the same Issue

  1. The origin of jadeitite-forming subduction-zone fluids: CL-guided SIMS oxygen-isotope and trace-element evidence
  2. Mineralogical characterization of the blue pigment of Michelangelo's fresco “The Last Judgment”
  3. Microstructure and magnetism in the ilmenite-hematite solid solution: A Monte Carlo simulation study
  4. Enhanced mass transfer through short-circuit diffusion: Growth of garnet reaction rims at eclogite facies conditions
  5. Behavior of H2O molecules in the channels of natrolite and scolecite: A Raman and IR spectroscopic investigation of hydrous microporous silicates
  6. Sound velocities and elastic constants of ZnAl2O4 spinel and implications for spinel-elasticity systematics
  7. The role of water in the synthesis of glaucophane
  8. On the connected porosity of mineral aggregates in crystalline rocks
  9. The reaction talc + forsterite = enstatite + H2O revisited: Application of conventional and novel experimental techniques and derivation of revised thermodynamic properties
  10. Ba(NpO2)(PO4)(H2O), its relationship to the uranophane group, and implications for Np incorporation in uranyl minerals
  11. High-pressure phase transitions and hydrogen incorporation into MgSiO3 enstatite
  12. High-pressure Raman spectroscopic studies of hydrous wadsleyite II
  13. Carbonate reduction by Fe-S-O melts at high pressure and high temperature
  14. Cancrinite: Crystal structure, phase transitions, and dehydration behavior with temperature
  15. On the structure of palygorskite by mid- and near-infrared spectroscopy
  16. Free energy of formation of zircon and hafnon
  17. In-situ AFM study of smectite dissolution under alkaline conditions at room temperature
  18. Angular dependence of potassium K-edge XANES spectra of trioctahedral micas: Significance for the determination of the local structure and electronic behavior of the interlayer site
  19. Mössbauer characterization of upper mantle ferrikaersutite
  20. The crystal structure of piergorite-(Ce), Ca8Ce2(Al0.5 Fe3+ 0.5)Σ1(□,Li,Be)2Si6B8O36(OH,F)2: A new borosilicate from Vetralla, Italy, with a modified hellandite-type chain
  21. Native gold and native copper grains enclosed by olivine phenocrysts in a picrite lava of the Emeishan large igneous province, SW China
  22. Comprehensive chemical analyses of a cordierite from Kiranur, South India, and of an ilvaite from Serifos, Greece: Two new microprobe reference samples
  23. Vibrational spectroscopy of brucite: A molecular simulation investigation
  24. Letter. Terrestrial analogs of martian sulfates: Major and minor element systematics of alunite-jarosite from Goldfield, Nevada
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