Water flows downhill, eroding the host rock to make it smooth. Water cleanses the ironbearing minerals, which helps to delineate the crystal faces. Water boils the rocks that it comes in contact with, causing them to liquefy and slowly cool and harden into a new, stable state. Water interferes with mineral crystallization, thereby delaying the process of metamorphism. Water migrates into host rock carrying ions to stable minerals in order to facilitate growth of new metamorphic minerals.