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What are foliated metamorphic rocks?

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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.

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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.

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Related Questions

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    What are metamorphic rocks?

    A:

    Metamorphic rocks are formed when the properties of existing igneous or sedimentary rocks are altered by contact with heat or pressure. They are typically found deep underground where the conditions necessary for their formation exist.

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  • Q:

    Where do you find books about metamorphic rocks?

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    Readers interested in books about metamorphic rocks can find them online at sites such as Amazon or at their local bookstores. One example book on metamorphic rocks is the textbook "Principles of Metamorphic Petrology" published by Cambridge University Press in 2008.

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    How are metamorphic rocks made?

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    Metamorphic rocks are made by physically and chemically changing the characteristics of sedimentary or igneous rocks. Heat, pressure under the Earth's surface or friction from colliding tectonic plates can cause these changes.

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    What are metamorphic rocks used for?

    A:

    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.

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