ABSTRACT: X-Ray diffraction, pétrographie microscopy and SEM analysis are used together to obtain qualitative aod quantitative information on the microstucture of kaoilinite-illite-quartz bodies,.. The pétrographie- microscope is used to analyse of the microstructure and mineralogy of the fired products. Bur the results have not been entirely satisfactory because of the inability to detect crystalline particles, of submicrometer mulHte, cristobalite and pores, The. body consists of mullite cristobalite and quartz (crystalline phases) in a composite structure where crystals and porosity are embedded in the matrix of amorphous/glassy phase.. Both glass and amorphous phases .appear in more or less significant amounts in all the studied fired clay bodies., The presence of quartz, detrital mica, and Ca- Na feldspar indicate bodies-being usually fired under nonequlibrium conditions and that many chemical reactions do not go to completion because of the lack of sufficient, heat treatment and of intimate contact of the constituents. If the reactions were allowed to go to completion this would result in a large glassy phase that would endanger the desirable properties of the clay based ceramic bodies.