Ca<sub>3</sub>SiO<sub>4</sub>Cl<sub>2</sub>—An Anthropogenic Phase from Burnt Mine Dumps of the Chelyabinsk Coal Basin: Crystal Structure Refinement, Spectroscopic Study and Thermal Evolution
Anastasia S. Brazhnikova,
Margarita S. Avdontceva,
Andrey A. Zolotarev,
Maria G. Krzhizhanovskaya,
Vladimir N. Bocharov,
Vladimir V. Shilovskikh,
Mikhail A. Rassomakhin,
Vladislav V. Gurzhiy,
Sergey V. Krivovichev
Affiliations
Anastasia S. Brazhnikova
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Margarita S. Avdontceva
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Andrey A. Zolotarev
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Maria G. Krzhizhanovskaya
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Vladimir N. Bocharov
Centre for Geo-Environmental Research and Modelling, St. Petersburg State University, Ulyanovskaya St., 1, 198504 St. Petersburg, Russia
Vladimir V. Shilovskikh
Centre for Geo-Environmental Research and Modelling, St. Petersburg State University, Ulyanovskaya St., 1, 198504 St. Petersburg, Russia
Mikhail A. Rassomakhin
South Urals Federal Research Center of Mineralogy and Geoecology of Ural Branch of the Russian Academy of Sciences, 456317 Miass, Russia
Vladislav V. Gurzhiy
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Sergey V. Krivovichev
Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
The mineral-like phase Ca3SiO4Cl2, an anthropogenic anhydrous calcium chlorine-silicate from the Chelyabinsk coal basin has been investigated using single-crystal and high-temperature powder X-ray diffraction and Raman spectroscopy. The empirical formula of this phase was calculated as Ca2.96[(Si0.98P0.03)Σ1.01O4]Cl2, in good agreement with its ideal formula. Ca3SiO4Cl2 is monoclinic, space group P21/c, Z = 4, a = 9.8367(6) Å, b = 6.7159(4) Å, c = 10.8738(7) Å, β = 105.735(6)°, V = 691.43(8) Å3. The crystal structure is based upon the pseudo-layers formed by Ca–O and Si–O bonds separated by Cl atoms. The pseudo-layers are parallel to the (100) plane. The crystal structure of Ca3SiO4Cl2 was refined (R1 = 0.037) and stable up to 660 °C; it expands anisotropically with the direction of the strongest thermal expansion close to parallel to the [−101] direction, which can be explained by the combination of thermal expansion and shear deformations that involves the ‘gliding’ of the Ca silicate layers relative to each other. The Raman spectrum of the compound contains the following bands (cm–1): 950 (ν3), 848 (ν1), 600 (ν4), 466 (ν2), 372 (ν2). The bands near 100–200 cm−1 can be described as lattice modes. The compound had also been found under natural conditions in association with chlorellestadite.
