Refined crystal structure of parakeldyshite and the genetic crystal chemistry of zirconium minerals with [Si2O7] diorthogroups |
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| Authors: | I. V. Pekov N. V. Zubkova D. Yu. Pushcharovsky U. Kolitsch E. Tillmanns |
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| Affiliation: | 1.Faculty of Geology,Lomonosov Moscow State University,Leninskie gory, Moscow,Russia;2.Institüt für Mineralogie und Kristallographie,Universit?t Wien,Wien,Austria |
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| Abstract: | The structure of the mineral parakeldyshite Na1.93ZrSi2O6.93(OH)0.07 is refined by X-ray diffraction analysis. The main crystallographic data are as follows: space group P (overline 1 ), a = 6.617(2) Å, b = 8.813(1) Å, c = 5.426(1) Å, α = 87.26(3)°, β = 85.68(3)°, γ = 71.45(3)°, and R F = 0.0153. The initial structural model of this mineral is confirmed. Within this model, the structure of parakeldyshite is based on the heteropolyhedral framework formed by [Si2O7] diorthogroups, which are linked together through isolated zirconium octahedra. The fundamental difference between the structure under investigation and the initial structural model is associated with the arrangement of the extraframework cations. A comparative crystal chemical analysis of the zirconium silicates with [Si2O7] diorthogroups is performed. |
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