Fluorellestadite from burned coal dumps:crystal structure refinement, vibrational spectroscopy data and thermal behavior

Margarita S. Avdontceva, Andrey A. Zolotarev, Sergey V. Krivovichev, Maria G. Krzhizhanovskaya, Ella V. Sokol, Svetlana N. Kokh, Vladimir N. Bocharov, Mikhail A. Rassomakhin, Anatoly A. Zolotarev

Research output: Contribution to journalArticlepeer-review

Abstract

Nine different samples of fluorellestadite from Chelyabinsk, Kizel and Kuznetsk coal basins were studied by single-crystal X-ray diffraction analysis, thermal X-ray diffraction (25–800 °C), Infrared (IR) and Raman spectroscopy. Fluorellestadite is hexagonal, space group P63/m, the unit-cell parameters for the nine samples studied vary within rather small ranges: a = 9.415(5) – 9.4808(7) Å, c = 6.906(2) – 6.938(8) Å, V = 530.3(4) – 538.41(9) Å3. The mineral is isotypic with apatite, the structure is based upon isolated TO4 tetrahedra, where the T position is statistically occupied by Si4+ and S6+ with the ideal ratio Si:S equal to 1:1. The fluorine atoms are located in channels of the Ca4[(S,Si)O4]6 framework oriented parallel to the c axis. The thermal expansion of fluorellestadite is almost isotropic in the temperature range 25–800 °C (for ambient temperature: αa = 12.0·10−6 °C−1, αc = 11.9·10−6 °C−1; for 800 °C: αa = 18.2·10−6 °C−1, αc = 18.6·10−6 °C−1). A similar thermal behavior had been observed for fluorapatite. Despite the same structure motifs and close conditions of formation, the samples of fluorellestadite show different S/Si/P occupancies for T site and the F/Cl/OH (X-position) ratios.

Original languageEnglish
Number of pages11
JournalMineralogy and Petrology
DOIs
StatePublished - 18 Feb 2021

Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Keywords

  • apatite supergroup
  • burned coal dumps
  • Chelyabinsk coal basin
  • Fluorellestadite
  • technogenic (anthropogenic) mineralogy

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