Rare Li–Mg micas, taeniolite [KLiMg₂(Si₄O₁₀)(F, OH)₂ ] and its variety spodiophyllite [KLi_0.5Mg_2.5(Si_3.5Al_0.5O₁₀)(F, OH)₂ ], which were erroneously identified earlier as Li-bearing phlogopite, were found for the first time in massive and veinlet-type ores of the Ermakovsk F–Be deposit. The composition of these micas was determined by a combination of electron microprobe analysis, X-ray diffraction, and flame photometry. The distribution of these minerals was also analyzed. They are confined to ores of only one of the studied ore zones, although the major ore mineralogy and chemistry of mineralizing solutions were similar in all ore zones. The solutions that produced taeniolite and spodiophyllite had elevated alkalinity, which could cause relatively low Be contents in these solutions.

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