 Other crystalline rocks, the metamorphic rocks such as marbles, mica-schists and quartzites, are recrystallized.This means that they were at first fragmental rocks like limestone, shale and sandstone and have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state.Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins.