1. Coral Growth: Millions of years ago, during the Devonian period (about 419 to 359 million years ago), warm, shallow seas covered much of Michigan. In these seas, colonies of coral thrived, building up reefs. The coral species that forms Petoskey stones, Hexagonaria percarinata, had a distinctive hexagonal shape.
2. Death and Burial: Over time, the coral died and the colonies were buried under layers of sediment, primarily limestone and dolomite.
3. Fossil Formation: The organic material of the coral was slowly replaced by minerals from the surrounding sediment. This process is called diagenesis, and it preserved the coral's structure in the form of a fossil.
4. Glacial Erosion: During the last ice age, glaciers scraped across the landscape, eroding and carrying away the rock layers, including the fossilized coral.
5. Deposition and Weathering: As the glaciers retreated, they deposited the rock debris they carried, including the Petoskey stone fossils, in new locations. Over time, these fossils were exposed to the elements, weathered, and smoothed by water and wind.
6. Discovery: Today, Petoskey stones can be found along the shores of Lake Michigan and other areas where glacial deposits are present. Their distinctive hexagonal pattern, resembling a honeycomb, makes them easy to identify.
In short, Petoskey stones are fossils formed by the fossilization of ancient coral, followed by glacial erosion and deposition.
