Abstract
Technogenic steklite, KAl(SO4)2, and unnamed mineral phase (K,Na)3Na3(Fe,Al)2(SO4)6 from burnt dumps of the Chelyabinsk Coal Basin have been investigated by single-crystal X-ray diffraction and electron microprobe analysis. Steklite is trigonal, space group P3¯, a = 4.7277(3), c = 7.9871(5) Å, V = 154.60(2) Å3. The crystal structure was refined to R1 = 0.026 (wR2 = 0.068). It is based upon the [Al(SO4)2]− layers formed by corner sharing of SO4 tetrahedra and AlO6 polyhedra. The anionic [Al(SO4)2]− layers are parallel to the (001) plane and linked via interlayer K+ ions. The regular octahedral coordination of Al is observed that distinguishes technogenic steklite from that found in Tolbachik fumaroles. The (K,Na)3Na3(Fe,Al)2(SO4)6 phase is trigonal, space group R3¯, a = 13.932(2), c = 17.992(2) Å, V = 3024.4(7) Å3, R1 = 0.073 (wR2 = 0.108). The crystal structure is based upon the anionic chains [(Fe,Al)(SO4)3]3− running parallel to the c axis and interconnected via K+ and Na+ ions. There are no known minerals or synthetic compounds isotypic to (K,Na)3Na3(Fe,Al)2(SO4)6, due to the presence of separate K and Na sites in its structure.
Highlights
This study is a continuation of the series of our publications devoted to the specific features of the crystal chemistry of technogenic minerals from burnt dumps of the Chelyabinsk Coal Basin [1,2,3,4,5].Here, we report, in detail, the features of two alkali-bearing Al–Fe sulfates crystallized from gaseous phases in high-temperature technogenic environments.In general, sulfates constitute one of the most important classes of minerals which contains numerous species diverse from both chemical and structural points of view [6]
The regular octahedral coordination of Al is observed that distinguishes technogenic steklite from that found in Tolbachik fumaroles
The most interesting aspect of the crystal structure of steklite studied here is related to the shape of the AlO6 polyhedra
Summary
This study is a continuation of the series of our publications devoted to the specific features of the crystal chemistry of technogenic minerals from burnt dumps of the Chelyabinsk Coal Basin [1,2,3,4,5].Here, we report, in detail, the features of two alkali-bearing Al–Fe sulfates crystallized from gaseous phases in high-temperature technogenic environments.In general, sulfates constitute one of the most important classes of minerals which contains numerous species diverse from both chemical and structural points of view [6]. This study is a continuation of the series of our publications devoted to the specific features of the crystal chemistry of technogenic minerals from burnt dumps of the Chelyabinsk Coal Basin [1,2,3,4,5]. We report, in detail, the features of two alkali-bearing Al–Fe sulfates crystallized from gaseous phases in high-temperature technogenic environments. The technogenic sulfates formed at burning dumps of coal mines are close in their genetic features to purely natural sulfates crystallizing in oxidizing-type volcanic fumaroles (for recent discoveries, see [7,8,9,10,11]). B.V. Chesnokov in 1991 as a new mineral species from burnt dumps of coal mines of the Chelyabinsk
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