Abstract
Lobanovite from the Koashva mountain in the Kibiny massif (Kola Peninsula) has been studied by methods of X-ray-spectral microanalysis, monocrystal X-ray diffractometry and IR-spectroscopy. Parameters of the lobanovite monoclinic unit cell: a = 5.3329(1), b = 23.1500(5), c = 10.3844(2) Å, β = 99.640(2)°, V = 1263.92(4) Å3; space group C2/m; crystal structure was refined to R = 2.8% with use of 1918 reflections with I 3σ(I). Crystal-chemical formula is as following (Z = 2): A(K0.93Ba0.01□0.06)2 B(Na0.95Ca0.05) [M1Na M2 (Mn0.445Fe2+0.275Na0.115Fe3+0.1Ca0.065)2 M3(Fe2+0.525Mg0.375Fe3+0.1)2 M4(Mg0.57Fe2+0.33Fe3+0.1)2 (OH)4] [D(Ti0.885Fe3+0.09Nb0.025)O(Si4O12)(ОН)0.1]2. In general, the studied sample of lobanovite is close to previously described ones, but it characterized by supplementary splitting in several bands if IR-spectrum. In D-position, together with titanium, there were for the first time revealed admixtures of iron and niobium, and in the inter-packet spаce – the partial replacement of sodium and potassium cations by barium and calcium. These facts were not mentioned in earlier publications. The article displays also some chemical and IR-spectroscopic data about {-ray-amorphous karnasurtite-like silicate and a rare-earths phosphate associated with lobanovite.
Published Version
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