The time-dependent radial distribution of Al₂O₃ and silicate dust (expressed as condensation fractions of Al and Si, respectively) in model An315u3, zoomed in on the inner edge of the circumstellar dust shell (snapshots of 100 pulsation phases). The blue area (showing a similar shape in all panels) corresponds to Fe-free silicates (Mg₂SiO₄). The red curves (covering different areas in the 3 panels) represent Al₂O₃ (treated here as passive, separate grains) for different grain temperatures, resulting from the high-k optical data set (top), the low-k data (bottom), and the assumption of Al₂O₃ grain temperatures being equal to those of Mg₂SiO₄ grains of comparable sizes (middle).