What is a Petoskey Stone?

Polished Petoskey Stone Coral Fossil (Hexagonaria, percarinata)

Simply put, a Petoskey Stone is an extinct fossilized coral. Why is it called, “Petoskey Stone”? Because they are found in abundance in and around Lake Michigan shores, especially near the Northern Michigan city of Petoskey (USA)! The name “Petoskey” is the English adaptation of an Ottawa Indian Chief Petosegay, which is said to mean “The Rising Sun”!

They are also called “lucky stones” by many!

How could the remains of a coral, which thrived in tropical warm waters, possibly find its way to the cool regions of Michigan?

During the prehistoric Devonian time period in which they lived, around 416 to 369 million years ago, the dominant landscape of North America was tropical. Consequently, warm shallow seas covered a large portion of the continent, including Michigan. Later, the corals were buried under deep layers of sediment. Many millions of years after that, when the great glaciers retreated, they scraped and dug into those forgotten layers of earth. The glaciers deposited them where we can now enjoy the good fortune of discovering their mysteries.

Rough unpolished Petoskey Stone Coral Fossil (Hexagonaria, percarinata) found on Lake Michigan beaches.

Petoskey Stone fossils originate from mass coral colonies of Hexagonaria, percarinata. Each hexagonal corallite (visible in the stone) held a single animal which opened a mouth exposing tentacles that siphoned food particles floating by in ocean currents. The tentacles were also used to sting any organism or other corallites that came too close. Calcite, silica and other minerals replaced the original exoskeleton over many millions of years.

Corallites Detail of Petoskey Stone Coral Fossil (Hexagonaria, percarinata) found on Lake Michigan Beach

PETOSKEY STONE CLASSIFICATION

Common Name: Petoskey Stone or Lucky Stone

Scientific Name: Hexagonaria, percarinata

Kingdom: Animalia

Phylum: Cnidardia (means to sting)

Class: Anthozoa (ie coral, sea pens, sea anemones)

Subclass: Zoantharia (true corals)

Order: Rugosa (means wrinkled wall)

Family: Hexagonaria (means six sides)

Species: percarinata

Petoskey Stone Coral (Hexagonaria, percarinata) Rendering Drawing of Living Sample

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