Results of a study on ultrabasic rock weathering under subtropical climate are presented. The mineralogical evolution leads to the formation of nontronite and amorphous materials from the wrathering of mafic-silicates, while the plagioclase, in the same rock, yields kaolinite and montmorilonite. The transformation of amorphous materials into goethite occurs in the soil and the clay minerals are preserved as aluminous nontronite.The weathering action leads to strong loss of Mg and Ca, with partial retention of Si. Mg loss is more intense than that of Ca when both are components of silicates. If Ca is a carbonate component, as occurs in the serpentinites, its mobilization is quicker than that of Mg. Fe can be partially mobilized when it is contained in mafic silicates, but when it is a component of magnetite, as in serpentinites, Fe becomes absolutely fixed. Al and Ti are flxed. Mn, Cr, Ni, Co, V and Cu have the same behavior as Fe. Na behaves as Ca. During the first stages of weathering, K is lost, but it is fixed again in the soil by organic compounds and clay minerals.The groundwater and supergenic mineral compositions are in equilibrium, and both indicate a sialferrtzation weathering type. The relative mobilities, based on the groundwater composition, show some differences as compared to the mobilities based on the use of the solid phase composition. Such differences are caused by some imprecisions in the methods themselves.Results of a study on ultrabasic rock weathering under subtropical climate are presented. The mineralogical evolution leads to the formation of nontronite and amorphous materials from the wrathering of mafic-silicates, while the plagioclase, in the same rock, yields kaolinite and montmorilonite. The transformation of amorphous materials into goethite occurs in the soil and the clay minerals are preserved as aluminous nontronite.The weathering action leads to strong loss of Mg and Ca, with partial retention of Si. Mg loss is more intense than that of Ca when both are components of silicates. If Ca is a carbonate component, as occurs in the serpentinites, its mobilization is quicker than that of Mg. Fe can be partially mobilized when it is contained in mafic silicates, but when it is a component of magnetite, as in serpentinites, Fe becomes absolutely fixed. Al and Ti are flxed. Mn, Cr, Ni, Co, V and Cu have the same behavior as Fe. Na behaves as Ca. During the first stages of weathering, K is lost, but it is fixed again in the soil by organic compounds and clay minerals.The groundwater and supergenic mineral compositions are in equilibrium, and both indicate a sialferrtzation weathering type. The relative mobilities, based on the groundwater composition, show some differences as compared to the mobilities based on the use of the solid phase composition. Such differences are caused by some imprecisions in the methods themselves.