Mineralogical and technological properties of the Konya clays, Central Turkey

Konya clay occurrence is the biggest clay mine of Turkey, except for the Şile region (İstanbul, Turkey) clays, and crop out near the Doğanhisar (Konya, Central Turkey). It was formed by alteration of the Na- and K-feldspars, and muscovitic micas; additionally, direct transportation of the sericitic/illitic clays from the metapelitic rocks of metamorphic basement into the Neogene depositional basin. X-ray diffraction (XRD) studies revealed that major constituents of the Konya clays are the quartz, kaolinite and illite with the subordinate amount of paragonitic mica, pyrite, rutile and the organic materials (lignite, peat). The main purpose of this study is to determine the ceramic properties of Konya clays fired at various temperatures. For this aim, the chemical and mineralogical composition of clays was determined by X-ray fluorescence (XRF) and XRD. Thermal analysis techniques are used to measure the physical changes on heating, namely differential thermal analysis (DTA) and thermo-gravimetric analysis (TG). Test samples have been prepared by pressing and firing in the range of 900–1200 °C. Linear shrinkage, water absorption, flexural strength and color values were done in order to characterize clays after firing. Particularly between 1150 and 1200 °C, a significant decrease was observed in water absorption values. All studied samples seem to be easily adaptable for dry pressing ceramic process. In particular, kaolinite and illite rich samples show the best technological behaviors. The addition of Konya clays could have been used in wall, floor and porcelain stoneware tiles and sanitaryware ceramic products.