Crystal chemistry of pyroaurite from the Kovdor massif (Kola peninsula. Russia) and LSngban Fe-Mn Deposit (Varmland, Sweden)
Zhitova E. S., Ivanyuk G. Yu,, Krivovichev S. V., Yakovenchuk V.N.,Pakhonovsky Ya. Α.,Mikhaihva Yu. A.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2016. V. 145. N 3. P. 81-94
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Language: Russian
Abstract
Samples of pyroaurite [Mg6(ОН)16][(СО3)(Н2O)4] from the Kovdor massif (Kola Peninsula, Russia) and Långban deposit (Filipstad, Värmland, Sweden) were studied by single-crystal and powder X-ray diffraction, electron microprobe analysis and Raman spectroscopy. Both samples are rhombohedral, R¯3m, a = 3.126(3), c = 23.52(2) Å (Kovdor), and a = 3.1007(9), c = 23.34(1) (Långban). Powder X-ray diffraction revealed presence of only 3R polytype at the recorded pattern. M2+ : M3+ ratio was determined as 3.1—3.2 (Kovdor) and 3.0 (Långban). Raman band in 3500—3400 cm–1 confirms presence of water and/or hydroxyl groups in the composition, while bands at 1346 and 1058 cm–1 are characteristic for carbonate groups. On the base of obtained data, samples should be identified as pyroaurite-3R (the hydrotalcite group).
Key words: pyroaurite, Kovdor, Långban.
