Preparation of Oxides and Silicates. Both simple (SiO2, Al2O3,Mn3O4, and Fe3O4) and complex (K2O3 Al2O3 3 6SiO2) oxides were tested in this study. SiO2 of different crystallinity (amorphous,aphanitic or cryptocrystalline, and crystalline) came from a synthetic silicon oxide, an agate, and a quartz sand sample, respectively.Al2O3 was prepared from the mineral corundum. The original silica and alumina were ground using a mortar and pestle and separated into size fractions of