The Petoskey Stone is a coral that lived 350 million years
ago during the Devonian age when the northern part of Michigan was covered with a sea of warm water. The scientific name is
Hexagonaria percarinata; sloss (Hexagonaria meaning having six sides).
The
soft living tissue of the corallite was called polyp. At the center of the polyp was the food intake opening or mouth. This
dark spot, or the eye of the corallite, has been filled with silt or mud that petrified after falling into the openings. Surrounding
the opening were tentacles that were used for gathering food and drawing the food into the mouth. This living corallite thrived
on plankton which lived in the warm sea.
Calcite,
silica and other minerals have replaced the original elements in each cell. Each chamber or corallite at one time was a living
marine animal that grew in colonies. The Petoskey stone is also known as a colony coral.
