________ is typically formed by metamorphism of a sandstone.
Quartzite is a nonfoliated metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone, is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together.t is often difficult or impossible to differentiate quartz arenite from quartzite. The transition of sandstone into quartzite is a gradual process. A single rock unit such as the Tuscarora Sandstone might fully fit the definition of quartzite in some parts of its extent and be better called sandstone in other areas.