Recrystallization (geology)

In geology, solid-state recrystallization is a metamorphic process that occurs under temperature and pressure where atoms of a mineral are reorganized by diffusion and/or dislocation glide. The mineral composition may remain unchanged. This process can be illustrated by observing how snow recrystallizes to ice.
As opposed to metasomatism, which is a change in composition, recrystallization can be a purely physical process. 
Limestone is a sedimentary rock that undergoes metamorphic recrystallization to form marble, and clays can recrystallize to muscovite mica.