The weathering crust of granitic rocks in Antioquia, Colombia, can be divided into eleven zones. Since zone IX that has been formed by wind-bourne loess is not a weathering crust in situ, it was excluded from the study. Zones X and XI, being soil, were also excluded. The grain distribution was mechanically analyzed for the samples from zones V-VIII. The change from "masa" A (zone V) to "masa" B (zone VI) is characterized by transformation of pebble to sand, the change from "masa" B to red

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... (zone VII) is characterized by transformation of silt to clay and the change from red " masa" to "shimofuri" clay (zone VIII) which does not show noticeable alteration of the silt-size grains to clay-size grains is characterized by transformation only of sand to silt. Mineralogical composition of weathering zones are identified by the X-ray diffraction method. The presence of quartz was confirmed in all the weathering zones. K-feldspar begins to alter from weathered granite A (zone III) and completely disappears in "masa" A. Plagioclase and biotite disappearsalmost completely in the initial stage of weathering. Of the secondary minerals by the weathering action, chlorite, illite, halloysite and gibbsite are seen. The existence of kaolinite is observed very conspicuously in red "masa" and "shimofuri" clay. Chemical analysis was carried out by X-ray fluorescence spectrometer. The transfer of CaO and Na2O shows the tendency of decrease in a convex-shaped curve in the weathering crust in Japan but in a concave-shaped curve in Colombia.