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.Know More
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 used for roofing material, decorative gardening stone, the base for snooker tables, building material, sculpture material and paving material. Metamorphic rocks come in three different types: slate, marble and schist.Full Answer >
Metamorphic rocks can commonly be found in mountain ranges, like the Himalayas, Alps and Rocky Mountains. This is because metamorphic rocks form at the core of mountains from the intense pressure and heat. As mountains erode away over time, these types of rocks can be found on the surface.Full Answer >
Pressure that shapes rocks to align in particular directions causes foliation, according to the Mineralogical Society of America. When such differential pressure acts on the forming rocks, it produces layers of rocks that run in parallel to each other, creating the diagnostic banded appearance of foliated rocks.Full Answer >
Metamorphic rocks are most often found in mountainous regions though they can be seen wherever there are signs of geological upheaval in an area. This type of rock is formed by the transformation of another rock type, a change that is usually triggered by tremendous heat, pressure or other violent phenomena. The forces that cause metamorphic rocks to form are so great that they change not only the appearance but also the chemical composition of an existing rock.Full Answer >