Recrystallization is the process through which the preexisting crystals are destroyed, and later the material left of them crystallizes all over again and forms new crystal structures. Basically this process happens when a crystal structure is exposed to high temperatures and pressures, When that happens, the crystal structure falls apart, often being melted. After it is melted, the material will eventually start to cool off again. As it cools off, new crystals will start to form. What type of crystals will form will depend on the rate of cooling off, but also on the agent that destroyed the initial crystals, as it can mix with the material, gradually giving birth to a new crystal structure.
