Rocksday

Siltstone

Rock of silt — grains finer than sand but coarser than clay.

Siltstone specimen
Photo: Mike Davis, CC0, via Wikimedia Commons

How to identify siltstone

  • Grains too small to see but gritty against your teeth.
  • Thin layers, not as flaky as shale.
  • Dull and earthy.

Often confused with

Where it's found

  • Sedimentary basins worldwide
  • Grand Canyon (Supai Group)

Uses

Flagstone and building stone.

Rock tumbling

Not suitable for tumbling.

Did you know?

Geologists really do test siltstone versus mudstone by gently biting it.

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

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