Rocksday

Chert

A hard sedimentary rock of microscopic quartz. Dark nodules in chalk are called flint.

Chert specimen
Photo: Unknown, Public domain, via Wikimedia Commons

How to identify chert

  • Breaks with smooth, curved fractures and sharp edges.
  • Waxy luster on fresh breaks.
  • Scratches glass.
  • Sparks when struck against steel.

Often confused with

Where it's found

  • Flint Ridge, Ohio
  • Alibates, Texas
  • Chalk cliffs of southern England

Uses

Stone tools, fire-starting and gunflints.

Rock tumbling

Great for tumbling.

Did you know?

Flint is Ohio's state gemstone; people quarried Flint Ridge for thousands of years.

Think you could spot it from a blurry close-up?

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