Some characteristics of quartz in pottery stones from various localities and its cristobalitization by firing have been examined by various methods. Specimens were prepared from the pottery stones by crushing, classifying to 10-37μm, and purifying by hot phosphoric acid and fluoric acid. Substitution of Al ion in quartz was confirmed from ESR and EPMA analyses. With the increase in the amount of Al2O3 substitution in quartz, following correlations were observed: (1) increase of unit cell volume, (2) increase of lattice strain, (3) lowering of α-β inversion temperature. Some specimens were found to be mixtures of quartz substituting different amounts of Al2O3. Cristobalitization from quartz in the pottery stones by firing was found to be correlated with the amount of Al2O3 substituted in quartz and a temperature at which quartz convert to cristobalite was lowered with the increase in the amount of substituted Al2O3. Larger amount of cristobalite was formed from the pottery stones with increasing the amount of Al2O3 substituted in quartz and with decreasing the amount of flux components in the pottery stones.
