Metamorphic quartz sandstone is a type of rock that forms when sandstone, a sedimentary rock composed mainly of quartz grains, undergoes metamorphism. Metamorphism is a process in which rocks are subjected to high temperatures and pressures deep within the Earth's crust. This process causes changes in the mineral composition and texture of the original rock.

Metamorphic quartz sandstone is typically harder and denser than its sedimentary counterpart. During metamorphism, the quartz grains in the sandstone recrystallize and grow larger, interlocking with each other to form a stronger and more cohesive rock. Additionally, impurities and other minerals in the original sandstone may react with each other or with the circulating metamorphic fluids to form new minerals. These metamorphic minerals can be found dispersed throughout the rock, giving it a different appearance and composition compared to the original sandstone.

The mineral composition and texture of metamorphic quartz sandstone can vary depending on the intensity and duration of the metamorphic conditions experienced. This means that a wide range of metamorphic quartz sandstone types can exist, each with distinct characteristics.