Petoskey Stone Fossil Value Guide

The Petoskey Stone is a unique fossilized colonial coral, Hexagonaria percarinata, that thrived in Michigan's warm Devonian seas 350 million years ago. These stones are highly collectible for their intricate hexagonal patterns, which represent the preserved skeletal structures of ancient coral polyps.

What affects the value of Petoskey Stone Fossil?

• Surface finish significantly impacts price, with professionally tumbled or hand-polished stones commanding higher values than raw specimens.
• The clarity and symmetry of the hexagonal 'sunburst' patterns determine the aesthetic desirability for collectors.
• Size is a primary factor, with larger, unbroken specimens weighing several pounds being more valuable than small pebbles.
• The presence of unique mineral inclusions or rare preservation of the coral's internal structure can increase market interest.

How to Identify Petoskey Stone Fossil?

• Look for the distinct 'six-sided' hexagonal pattern across the surface, which becomes highly visible when the stone is wet or polished.
• Verify the material is calcite-based; authentic stones will react to a small drop of white vinegar with slight bubbling.
• Check for a dark 'eye' or center in each hexagonal cell, which represents the original position of the coral polyp.
• Authentic specimens are primarily found along the shores of Lake Michigan and the northern Lower Peninsula of Michigan.

History of Petoskey Stone Fossil

Petoskey stones are fossils of Hexagonaria percarinata, an extinct species of colonial coral that lived during the Devonian period, approximately 350 million years ago. These corals thrived in warm, shallow seas. When the corals died, their calcium carbonate skeletons were preserved. During the last glacial period, glaciers scraped Michigan's bedrock, breaking off pieces of these fossilized corals and scattering them across the northern Lower Peninsula. The distinctive hexagonal patterns are the cross-sections of the individual coral polyps. In 1965, the Petoskey stone was designated as the state stone of Michigan.