The  kaolinization  of bauxite has  generally been thought  to be  a  simple process of epigenetic resilification. A study of the karstic boehmitic bauxites in the Vlasenica region of Yugoslavia, however, shows that  kaolinization took place in  a rather complex manner, in which the  alteration was  caused by the  percolation of siliceous water descending  through  the deposit by means  of cracks,  fissures, etc.