A sugilite-type double 6-membered ring (D6MR) silicate, Fe2Na2KLi3Si12O30 could be obtained for the first time under mild hydrothermal conditions. Impedance spectra revealed a bulk conductivity of 1.2 × 10−5 S cm−1 at 923 K. Hopping pathways of Li+ and Na+ were indicated in difference Fourier (ΔF) maps parallel to the D6MRs network using neutron powder diffraction at 298–1123 K. The current study presents a promising prototype for combined 2-dimensional Li+/Na+-ionic conductors with crystal-chemical flexibility and thermally high stability. A 2D network of pathways for conducting Li+ in Fe2Na2KLi3Si12O30 Display omitted •Combined Li+/Na+ ionic conductivity in Fe2Na2KLi3Si12O30.•Hydrothermal synthesis of Fe-rich sugilite counterpart at 503 K.•2D conducting pathways for Li+/Na+ are explained by neutron powder diffraction.•Impedance spectroscopic investigation.