Abstract
Electron energy loss measurements have been made up to 40 eV on specimens of several members of the mica group and quartz. By means of a Kramers-Kronig analysis the dielectric functions epsilon 1 and epsilon 2 have been deduced from the energy loss function. The excitations observed in mica and quartz are discussed with respect to the basic crystal structure (SiO4 tetrahedra) of both materials.