A face-centered icosahedral (FCI) quasicrystalline phase has been obse
rved in as-cast Mg-Zn-Y-Zr alloys. Selected-area electron diffraction
patterns (EDPs) have been studied and simulated. The conventional meth
od of computer plotting the stereographic projection diagrams of the K
ikuchi line distribution has been extended to the case of icosahedral
quasicrystalline phases (I-phases).