High-temperature hydrothermal alteration (see hydrothermal activity) and replacement of feldspars, to varying degrees, to form a fine-grained aggregate of the mineral kaolinite. Kaolinitization in granites can be so complete that the rock is reduced to a rotten, friable condition, quartz being the only mineral to survive the process unscathed. In this condition, the altered granite can be easily broken down by a high-pressure water jet and the kaolinite settled out from suspension in settling pools to produce china clay (kaolin) concentrates. See also chinastone.
Subjects: Earth Sciences and Geography.