5.9" Polished Slab Petoskey Stone Hexagonaria Coral Fossil Devonian Age Michigan
Location: Michigan, United States
Weight: 6.2 Ounces
Dimensions: 5.9 Inches Long, 2.2 Inches Wide, 1.1 Inches Thick
The item pictured is the one you will receive.
Devonian Age, 350 million years old
Petoskey Stone is a unique rock and fossil, specifically a fossilized rugose coral known as Hexagonaria percarinata. These stones are typically pebble-shaped and are found primarily in the northwestern and northeastern regions of Michigan's Lower Peninsula. They are fragments of a coral reef that existed during the Devonian period, approximately 350 million years ago.
Petoskey stones were formed through glaciation, when ice sheets plucked stones from the bedrock, grinding off their rough edges and depositing them in new locations. When dry, these stones may appear to be ordinary limestone, but when wet or polished, they reveal a distinctive mottled pattern of six-sided coral fossils.
The fossilized coral, Hexagonaria percarinata, is made up of tightly packed, six-sided corallites, which are the skeletal remains of once-living coral polyps. The center of each polyp served as its mouth, with tentacles extending outward to capture food. The hexagonal shape of each cell and the thin radial lines radiating from the dark central “eye” are unique features that make these fossils instantly recognizable.
Petoskey stones can be found on beaches and inland locations throughout Michigan, with some of the most popular beaches stretching from Traverse City to Petoskey along Lake Michigan. The movement of frozen lake ice during the winter often exposes new stones in the spring, making this the prime time for collectors. Well-known sites include Petoskey State Park, Magnus City Park Beach, and Solanus Mission Beach. Rockhounds also search cut roadbeds, gravel pits, and farmers’ fields.
The best time to find Petoskey stones is typically in spring, after ice and seasonal changes have shifted the shoreline, revealing fresh specimens for collection.
