The mineralogical composition of soils formed on phyllite and alluvium as well as examination of their mineral weathering characteristics should provide an insight into the stage of weathering. Three soil profiles from mountain, plain and low lands were selected. Based on XRD analysis, clay fractions were dominated by chlorite–vermiculite, vermiculite, HIV, illite, mica–vermiculite or mica-smectite. Persistance of 13.9 Å peak on
550 °C treated specimens indicate discrete chlorite, however, presence of 12.2 Å peak  on 550 °C pattern, further suggesting partial, random removal of interlayer hydroxide sheets and then, interstratified chlorite-vermiculite formation. Therefore, decrease in chlorite and illite is accompanied by increasing vermiculite in surface horizon. Higher intensity of even-ordered reflections (002,004) than odd ordered reflections (001,003) in chlorites revealed the presence of iron ions which further increased the susceptibility of them to chemical weathering through oxidation process and caused to degrade the interlayer sheets. The shoulder on the low angle side of 10 Å peak upon 550 °C pattern and on the high angle side of 14 Å peak under glycol solvation as well as gradual decrease in 14 Å peak intensity and gradual enhancement in 10 Å peak intensity at higher temperature may confirm Al- polymers within the interlayered space and HIV formation. Consequently, presence of mixed layer mineals indicate  the effect of acid – leaching weathering  on clay mineral transformation.