Eight xeralfs from the province of Jaen in the region of Andalusia (southern Spain) were studied. The micromorphology and mineralogy of the clay and sand fractions from the Bt horizon, among other characteristics, were investigated, and indices of pedogenic evolution, including relative redness index, relative development index of color and the relative development index of color + structure, clay illuviation index, anisotropy index for clay content, iron release index and kaolinite/smectite ratio, were calculated. These findings were supported by the results of factorial analysis (R mode) and correlation between variables. We found micromorphological evidence of clay illuviation (even in calcareous soils), alterations leading to clay formation, argillopedoturbation, coating disruption by carbonates, and polycyclicity. The clay fraction was essentially illitic, with smaller amounts of kaolinite, smectite and interstratified phases. Alterations were therefore moderate. Numerical estimators of evolution were informative of some specific pedogenic processes, and confirmed the influence of certain soil formation factors and the relative degree of evolution of different soils. The soil system comprising the xeralfs can be defined in terms of four factors that grouped the soil variables, and accounted for more than 90% of the variance: Factor 1, pedological development of the Bt horizon; Factor 2, a mineralogical factor; Factor 3, clay translocation in the profile; and Factor 4, a mineralogenetic feature of the Bt horizon.