Abstract
Abstract. This paper reports the first description of the crystal structure and crystal chemical features of fluorcarletonite, a new mineral from the Murun potassium alkaline complex (Russia), obtained by means of single-crystal and powder X-ray diffraction (XRD), electron microprobe analysis (EMPA), thermogravimetry (TG), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. The crystal structure of fluorcarletonite, KNa4Ca4Si8O18(CO3)4(F,OH)⚫ H2O, a rare phyllosilicate mineral, contains infinite double-silicate layers composed of interconnected four- and eight-membered rings of SiO4 tetrahedra and connected through the interlayer K-, Na- and Ca-centered polyhedra and CO3 triangles. The X-ray diffraction analysis confirms the mineral to be tetragonal, P4∕mbm, a=13.219(1) Å, c=16.707(2) Å, V=2919.4(6) Å3 (powder XRD data), a=13.1808(5) Å, c=16.6980(8) Å, V=2901.0(3) Å3 (single-crystal XRD data, 100 K). The EMPA (average from 10 analyses) gave the following composition (wt %): SiO2 44.1(6), CaO 20.0(3), Na2O 11.1(3), K2O 4.5(2), F 1.3(5), TiO2 0.1(1) and Al2O3 0.03(3). The TG–DSC analysis confirmed the presence of H2O and CO2 (weight losses of 1.17 % and 14.9 %, respectively). The FTIR spectrum acquired in the range from 4000 to 400 cm−1 reveals the presence of H2O, CO3 and OH groups. The average formula of fluorcarletonite calculated from the results of EMPA and crystal structure refinement is K1.04Na3.89Ca3.87Ti0.01Si7.99Al0.01O18(CO3)3.86(F0.72OH0.28)⚫1.11H2O.
Highlights
Fluorcarletonite, idealized KNa4Ca4Si8O18(CO3)4F q H2O, is the rare mineral belonging to the group of phyllosilicates
This paper reports the first description of the crystal structure and crystal chemical features of fluorcarletonite, a new mineral from the Murun potassium alkaline complex (Russia), obtained by means of single-crystal and powder X-ray diffraction (XRD), electron microprobe analysis (EMPA), thermogravimetry (TG), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy
This paper provides the first description of the crystal chemical features of fluorcarletonite from the Murun massif, Russia
Summary
Fluorcarletonite, idealized KNa4Ca4Si8O18(CO3)4F q H2O, is the rare mineral belonging to the group of phyllosilicates. In Chao (1972), it is reported that the ideal chemical formula of carletonite oshroKuNlda4bCe aw4Sriit8tOen18a(sCKON3)a44(OCaH4,SFi)8qOH182(OC1O+x3. Carletonite occurs either in pink to pale-blue prismatic crystals, in places up to 6 cm long, or as massive aggregates. E. Kaneva et al.: Fluorcarletonite from the Murun complex to find collectible specimens of carletonite in the Poudrette quarry, and prospects for the future are not promising, since the most interesting area, where the mineral has been found, was removed and allowed to flood (Pohwat and Cook, 2016). This paper provides the first description of the crystal chemical features of fluorcarletonite from the Murun massif, Russia. The holotype specimen has been deposited at the Sidorov State Mineralogical Museum of Irkutsk National Research Technical University (catalogue no. 12/1764)
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