Clay is a stony or earthy mineral aggregate composed of fine-grained minerals, which are plastic at appropriate water content and hardens up when fired. Clay soils have various mineral groups such as kaolinite, smectites, illites and palygorskite-sepiolite with unique properties for industrial applications. Uses of clay include manufacture of cement, tiles, ceramics, bricks, drilling clays, lead pencils, printing inks and paints. This project determined elemental and mineralogical composition of clays from Githima (00 46’ 40” S, 370 6’ 31”E), Kimathi (00 40’ 0”S, 370 10’ 28”E) and Ithanje (00 36’ 30” S, 370 6’ 46”E). The elemental and mineralogical composition were determined using AAS and XRD techniques respectively. The results indicated that clays composed of SiO2, Al2O3, and Fe2O3 as the major components in the following ranges of 40.80-55.40%, 16.27-30.33% and 3.90-20.53% for SiO2, Al2O3, and Fe2O3 respectively. Mineralogical results showed that the main mineral present in the clays were kaolinite, illite and quartz. Apparent porosity, linear shrinkage, bulk density, refractoriness and thermal shock resistance were 26.31-31.33%, 1-3 %, 1.56-1.68 g/cm3 1609-1686 0C and 20-26 cycles, respectively