Acta Musei Moraviae

Lithium-bearing micas from elbaite-subtype pegmatites in the Western Moravia, Czech Republic

Lithium-bearing micas from elbaite-subtype pegmatites of the Moldanubian Zone, western Moravia were examined using electron microprobe and the contents of Li₂O were calculated (method of TISCHENDORF et al. 1997). Very rare to minor Li-bearing micas occur in albite unit or in pockets as pink, pale violet to colorless small flakes or aggregates associated with schorl or elbaite. All studied samples exhibit Si = 7.11–7.89 apfu; this corresponds to ~60–90 mol. % of polylithionite component. Vacancy in the octahedral position suggests presence of dioctahedral mica (muscovite or hypothetical mica with Si = 8 apfu). The compositional evolution (Si, Al, F, Li_calc) implies increasing of polylithionite component during crystallization as in lepidolite-subtype pegmatites. Calculation of Li₂O (method of TISCHENDORF et al. 1997) is only approximate, it is not feasible for polylithionite-rich Li-bearing micas.