Metamorphic Rock, Reactions in a kaolinite-quartz system

A very simple mineralogical system and its response to changing pressure and temperature provide a good illustration of what occurs in metamorphism. An uncomplicated sediment at the Earth's surface, a mixture of the clay mineral kaolinite [Al4Si4O10(OH)8] and the mineral quartz (SiO2), provides a good example. Most sediments have small crystals or grain sizes but great porosity