In foliated metamorphic rocks, the compositon of the original rock is not apparent. This is true because as the heat and pressure have resulted in a recombination to form new minerals in the rock. The individual mineral grains may also be rearranged or rotated within the rock. Minerals may also recrystallize to form larger crystals. Three common foliated rocks are slate, gneiss and shcist.
Slate is formed by the metamorphsis of usually shale.
Because slate separates so easily along the bands of foliation, it is used to make roof and floor tiles. Schist is formed from more metamophism than a slate and has a compositon converted from basalt, granite sandstone and shale. Gneiss is formed by a high degree of metamorphism and has a composition similar to granite. Visit the Utah State 8th Grade Integrated Science Core Curriculum Page . USOE Home Page Copyright by the Utah State Office of Education.