Fig. 7. The structure of a mica, muscovite, (KF)2(Al2O3)3(SiO2)6(H2O). The space between the layers is occupied only by K+ ions. The layer structure facilitates cleavage to produce flat surfaces. Adapted from https://employees.csbsju.edu/cschaller/PrinciplesChem/network/NWalumina.htm (accessed 17th November 2020), courtesy of Chris Schaller.
