metamorphic rocks are formed by rocks being exposed to extreme heat and pressure
gneiss is metamorphic_rock. if_rock is very_hot_can_melt. slate is metamorphic_rock. marble is metamorphic_rock. amphibolite is metamorphic_rock. metamorphic_rock is rock. metamorphic_rock is stone. marble is useful_metamorphic_rock. marble is beautiful_metamorphic_rock. magma is rock.