Constitution of Fireclays at High Temperatures: II, Mineralogical Composition

Quantitative X‐ray diffraction analysis of quenched specimens, supplemented by HF solution and X‐ray fluorescence, was used to determine the mineralogical composition of three refractory clays after heating at 1150° to 1500°C. The three clays represent a range of purity found in high and superduty fireclay refractories: an impure plastic clay, a flint fireclay, and a kaolin. The results show the percentages of mullite, cristobalite, quartz, and liquid. The quantity and composition of the liquid phase were estimated by difference. Iron and titanium oxide impurities in the mullite decreased with increased firing temperatures.