A COMPARATIVE STUDY OF MINERALOGICAL TRANSFORMATIONS IN FIRED CLAYS FROM THE LABOYOS VALLEY, UPPER MAGDALENA BASIN (COLOMBIA)

mineralogical transformations during firing of clays from the laboyos valley at the upper magdalena basin (colombia) were studied. firing of clays was carried out in the temperature range 800-1200 °c under oxidizing conditions. the mineralogical transformations were investigated by x-ray diffraction (xrd) and scanning electron microscopy (sem). important compositional differences in the neoformed phases were observed in the clays. typical assemblages with quartz, illite, kaolinite, mica, halloysite, potassium feldspar and plagioclase were observed. several mineral phases were identified in the fired clays, with the reaction products including mullite, residual quartz, hematite, amorphous phase (glass generated by melting of feldspars and clays) in the fired clays.