DIFFERENTIAL THERMAL ANALYSES OF SOME MISSOURI FIRE CLAYS*

A bstract Differential thermal analyses were made of a large number of fire clays representative of Missouri production. Flint clays gave typical kaolinite curves. The curves of plastic and semiplastic clays were similar to that of kaolinite. Staining with aniline dyes, petrographic determination, and ceramic behavior indicate that clay minerals other than kaolinite are present in Missouri semiplastic clays but these (other clay minerals) were not revealed by the differential thermal method. High‐alumina hurley clays showed variously endothermic peaks of diaspore, boehmite, and kaolinite, but no exothermic peak which is characteristic of kaolinite.