Detailed chemical and structural studies were carried out for Li–Na–Fe-amphibole from cryolite rocks of the Katugin deposit, Transbaikalia. The rocks contain 30–70 vol.% cryolite, mafic minerals as Fe-silicates (Li–Na–Fe-amphibole, Li-containing fluorannite, and bafertisite), oxides (magnetite, ilmenite, pyrochlore, cassiterite, and others), and sulfides (sphalerite, pyrite, and chalcopyrite). Quartz, K-feldspar, polylithionite, REE-fluorides, and albite occur as minor or accessory phases. The chemical composition of amphibole (wt.%) varies as follows: SiO2, 48.5–48.9; TiO2, 0.4–0.8; Al2O3, 1.6–2.2; Fe2O3, 15.9–17.1; FeO, 17.6–18.4; MnO, 0.8–0.9; ZnO, 0.3–1.1; MgO, 0.2–0.3; CaO, <0.1; Na2O, 8.4–8.7; K2O, 1.4–1.5; Li2O, 0.6–0.8; H2O, 0.7–0.8; and F, 2.2–2.5. The amphibole has a specific composition intermediate among the F–Fe members of the Na-amphibole subgroup: 40–45 mol.% ferro-ferri-fluoro-nybøite, 40–45 mol.% ferro-ferri-fluoro-leakeite, and 10–20 mol.% fluoro-riebeckite ± fluoro-arfvedsonite. The mineral is monoclinic, space group C2/m, a = 9.7978(2), b = 17.9993(3), c = 5.33232(13) Å, β = 103.748(2)º, V = 913.43(3) Å3, and Z = 2. The structural formula of Li–Na–Fe-amphibole is (Na0.46K0.240.30)Na2.00(Fe0.952+Mg0.05)2⋅(Fe0.953+Ti0.025Mg0.025)2(Li0.37Fe0.482+Mn0.10Zn0.05)[(Si0.91Al0.09)4Si4O22](F0.58(OH)0.42)2. Raman and Mössbauer spectroscopy data are given for this amphibole.

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