Rocksday

Stromatolite

Layered mounds built by mats of microbes trapping sediment — among the oldest evidence of life.

Stromatolite specimen
Photo: Didier Descouens, CC BY-SA 4.0, via Wikimedia Commons

How to identify stromatolite

  • Wavy, domed, cabbage-like layers.
  • Fine laminations in cut sections.
  • Usually limestone or dolostone; fizzes.

Often confused with

Where it's found

  • Pilbara, Western Australia
  • Shark Bay, Western Australia
  • Glacier National Park, Montana

Uses

Scientific record of early life.

Rock tumbling

Can be tumbled with care.

Did you know?

Living stromatolites still grow in Shark Bay, Australia, much as they did 3 billion years ago.

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

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