Tinaksite and Tokkoite: X-ray Powder Diffraction, Optical, and Vibrational Properties

Abstract

In this study, natural tinaksite (K2Ca2NaTi[Si7O18OH]O) and tokkoite (K2Ca4[Si7O18OH](OH,F)) collected in charoite rocks of the Murun alkaline massif (Siberia, Russia) were examined by X-ray diffraction and optical and vibrational spectroscopic methods. A comparative analysis of the experimental diffraction patterns with respect to the calculated X-ray powder diffraction patterns was carried out for tinaksite and tokkoite powders. The shift in the diffraction peaks of tinaksite is explained by the smaller values of the unit cell parameters a and b as compared with those of tokkoite. A similar shift of the peaks is also observed in the Raman and infrared absorption spectra; however, this feature is explained by the difference in the chemical composition of the minerals. The shoulder in the absorption spectra at about 800 nm in tinaksite and 700 nm in tokkoite corresponds to the presence of Mn2+ and Fe3+ absorption bands, the presence of which determines the color of tinaksite and tokkoite. The luminescence band with a maximum at about 540–550 nm in the photoluminescence spectra is related to Mn2+ centers, while an additional band at about 610 nm can be associated with Ti3+ centers in tinaksite. The intensity of the Fe3+ ESR signal increases in both samples after heating, while the intensities of the bands associated with OH groups decrease in tinaksite and tokkoite. This characteristic is the result of iron oxidation and dehydrogenation reaction.

Nature and Isomorphism of Extra-Framework Components in Cancrinite- and Sodalite-Related Minerals: New Data

“…After irradiation of cancrinite, intense absorption bands appeared in its UV-Vis-near IR absorption spectrum near 16,100 cm −1 and in the range of 25,000-37,000 cm −1 , and a signal with g y = 2.014 and g x = 2.018 was observed in the ESR spectrum. It was shown in [27] that, in this case, the blue color and the ESR signal are due to the appearance of whole CO 3…”

Crossroads of vibrational (infrared and Raman) spectroscopy and X-ray powder diffraction in identification and characterization of some minerals – advantages and limitations. A review

“…Namely, reliable results can be obtained using X-ray powder diffraction, which make it possible to obtain good resolution of reflections, determine reliable values of unit cell parameters (comparable to those obtained by single-crystal X-ray diffraction), and carry out credible identification of structurally similar minerals. 12 Another advantage is that powder XRD can be done a mixture and using Rietveld analysis determine composition whereas single-crystal XRD requires a single phase.…”

High-temperature behaviour of fedorite, Na2.5(Ca4.5Na2.5)[Si16O38]F2⋅2.8H2O, from the Murun Alkaline Complex, Russia

“…Results from electron probe microanalysis (EPMA), differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) are also reported. This work follows other papers aimed at gaining insights on the crystal chemistry (Kaneva et al ., 2014, 2018, 2020b, 2021, 2022, 2023a, 2023b; Mesto et al ., 2014; Lacalamita et al ., 2017; Schingaro et al ., 2017; Lacalamita, 2018; Bogdanov et al ., 2021; Kaneva and Shendrik, 2022) as well as on the structural modifications of some rare minerals from Russian alkaline rocks under non-ambient conditions (Schingaro et al , 2018; Comboni et al , 2019; Lacalamita et al , 2019).…”