Rocksday

Petoskey Stone

A fossilized colonial coral, about 350 million years old, with a honeycomb of six-sided cells.

Petoskey Stone specimen
Photo: David J. Fred (Dfred), CC BY 3.0, via Wikimedia Commons

How to identify petoskey stone

  • Gray stones with a hexagonal honeycomb pattern.
  • Pattern shows best when wet.
  • Each cell has a dark center 'eye'.

Often confused with

Where it's found

  • Lake Michigan beaches near Petoskey, Michigan

Uses

Polished keepsakes and jewelry.

Rock tumbling

Can be tumbled with care. Soft — hand polishing is gentler.

Did you know?

It's Michigan's official state stone.

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

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