Chert

This content was prepared by Sarah Bingham, Rowan University Class of 2021

Chert is also an umbrella term

  • Chert is often used as an umbrella term for all microcrystalline quartz rocks

  • Flint and chert are sometimes considered interchangeable types

  • Flint occurs in chalk and is darker in color

  • Grey chert is lighter in color and occurs in limestone

  • Chert is considered lesser in quality

  • These impurities in the chert create the gray color

Why was it used for tools?

  • Chert is very hard

  • It fractures very cleanly

  • Breaks down a plane to create clean flakes

  • These flakes have very sharp edges

  • Also creates sparks when struck against iron

  • Chert could be used to start fires

What is Gray Chert?

  • A sedimentary rock that is a form of silicon dioxide (SiO₂) also known as quartz

  • Commonly found in carbonate rocks

  • Created as nodules of crystals congregate with water flow

  • Found in areas that used to be deep ocean beds

  • Can also be created from silicon skeletons of oceanic fossils

Where is it found in NJ?

  • Gray Chert is found in New Jersey's limestone deposits

  • The U.S. Geological Survey contains a full list of places where it has been documented including:

    • Allentown Dolomite

    • Buttermilk Falls Limestone

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