Foliated metamorphic rocks are rocks that have gone through extreme temperature and pressure changes, resulting in a different chemical composition. They are distinct for the appearance of a layered pattern throughout the rock.Continue Reading
Unlike non-foliated metamorphic rocks, which have a marbled appearance and form under uniform pressure, foliated metamorphic rocks form from uneven amounts of pressure. The areas of greatest pressure force minerals to line up, forming the layered bands throughout the rock.
Metamorphic rocks form beneath Earth's surface and move up to the surface through tectonic movement. The temperature range for metamorphism is between 200 and 800 degrees Celsius. The amount of heat and pressure that a metamorphic rock undergoes determines its grade. For example, slate, phyllite, schist and gneiss are grades of foliated metamorphic rocks. Slate forms under the lowest temperature and pressure changes, whereas gneiss experiences the highest temperature and pressure.
Slate, used as a material in roofing and pool tables, breaks into flat pieces. The layered bands in slate are less visible due to its fine grain texture. Phyllite contains more crystals than slate. Its layered bands often appear wrinkled or wavy. Schist, the grade between phyllite and gneiss, easily breaks into thin sections. Gneiss, pronounced “nice,” often contains feldspar or quartz. Its grain texture is coarse, making the layered bands of alternating minerals highly visible.Learn more about Geology
Metamorphic rocks are formed due to physical and chemical processes, such as heat, pressure and mineral exposure, that change the composition of pre-existing igneous, sedimentary and metamorphic rocks. These processes may be singular, but commonly occur simultaneously.Full Answer >
Rocks are classified by according to their mineral and chemical composition. There are three classifications for rocks: igneous, sedimentary and metamorphic.Full Answer >
Glass is not a mineral because it does not have a definite chemical composition, which means it does not always have the same chemical composition that can be expressed by a chemical formula. It also does not have a crystalline structure, so there is no specific order to the atoms.Full Answer >
Minerals are solid, naturally occurring, inorganic compounds that possess an orderly internal structure and a regular chemical composition. A mineral species has to possess these five characteristics to be regarded as scientifically valid.Full Answer >