Shale vs. Slate

By Jaxson

Main Difference

The main difference between Shale and Slate is that the Shale is a fine-grained, clastic sedimentary rock and Slate is a fine-grained, foliated, homogeneous, weakly metamorphic rock

  • Shale

    Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. It is the most common sedimentary rock.

  • Slate

    Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.The foliation in slate is called “slaty cleavage”. It is caused by strong compression causing fine grained clay flakes to regrow in planes perpendicular to the compression. When expertly “cut” by striking parallel to the foliation, with a specialized tool in the quarry, many slates will display a property called fissility, forming smooth flat sheets of stone which have long been used for roofing, floor tiles, and other purposes. Slate is frequently grey in color, especially when seen, en masse, covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green or cyan. Slate is not to be confused with shale, from which it may be formed, or schist.

    The word “slate” is also used for certain types of object made from slate rock. It may mean a single roofing tile made of slate, or a writing slate. They were traditionally a small, smooth piece of the rock, often framed in wood, used with chalk as a notepad or noticeboard, and especially for recording charges in pubs and inns. The phrases “clean slate” and “blank slate” come from this usage.

  • Shale (noun)

    A shell or husk; a cod or pod.

  • Shale (noun)

    A fine-grained sedimentary rock of a thin, laminated, and often friable, structure.

  • Shale (verb)

    To take off the shell or coat of.

  • Slate (noun)

    A fine-grained homogeneous sedimentary rock composed of clay or volcanic ash which has been metamorphosed so that it cleaves easily into thin layers.

  • Slate (noun)

    The bluish-grey colour of most slate.

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  • Slate (noun)

    A sheet of slate for writing on with chalk or with a thin rod of slate (a slate pencil) formerly commonly used by younger children for writing practice in schools.

  • Slate (noun)

    A roofing-tile made of slate.

  • Slate (noun)

    A record of money owed.

    “Put it on my slate – I’ll pay you next week.”

  • Slate (noun)

    A list of affiliated candidates for an election.

    “Roy Disney led the alternative slate of directors for the stockholder vote.”

  • Slate (noun)

    An artificial material resembling slate and used for the same purposes.

  • Slate (noun)

    A thin plate of any material; a flake.

  • Slate (adjective)

    Having the bluish-grey/gray colour of slate.

  • Slate (verb)

    To cover with slate.

    “The old church ledgers show that the roof was slated in 1775.”

  • Slate (verb)

    To criticise harshly.

    “The play was slated by the critics.”

  • Slate (verb)

    To schedule.

    “The election was slated for November 2nd.”

  • Slate (verb)

    To anticipate or strongly expect.

    “The next version of our software is slated to be the best release ever.”

  • Slate (verb)

    To set a dog upon (a person).

  • Shale (noun)

    soft finely stratified sedimentary rock that formed from consolidated mud or clay and can be split easily into fragile plates.

Oxford Dictionary

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