4.4" Polished Slab Petoskey Stone Hexagonaria Coral Fossil Devonian Age Michigan

Location: Michigan, United States

Weight: 3.8 Ounces   

Dimensions: 4.4 Inches Long, 3.8 Inches Wide, 0.2 Inches Thick 

The item pictured is the one you will receive.

Devonian Age, 350 million years old

Petoskey Stones are unique rocks that also serve as fossils, specifically of the rugose coral Hexagonaria percarinata. Typically pebble-shaped, these stones are found primarily in the northwestern and northeastern regions of Michigan’s Lower Peninsula. They are remnants of an ancient coral reef that thrived during the Devonian period, around 350 million years ago, preserving the intricate structure of the coral and offering a glimpse into Earth’s distant marine past.

Petoskey stones were formed through glacial activity, where advancing ice sheets plucked stones from the bedrock, smoothing rough edges and depositing them in specific locations. When dry, these stones may look like ordinary limestone, but when wet or polished, they reveal a distinctive mottled pattern of six-sided coral fossils.

The fossilized coral, Hexagonaria percarinata, consists of tightly packed, six-sided corallites, which are the skeletal remains of individual coral polyps. Each corallite’s center was once the mouth of the polyp, surrounded by tentacles that extended outward to capture food. The hexagonal shape of each cell, along with the thin radial lines emanating from the dark central “eye,” are unique features that make Petoskey stones instantly recognizable and highly prized by collectors.

Petoskey stones can be found on various beaches and inland locations in Michigan, with many of the most popular Petoskey stone beaches stretching from Traverse City to Petoskey along Lake Michigan. The movement of the frozen lake ice during the winters is thought to expose new stones each spring. Popular locations for finding these stones 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 them is often in the spring after the ice has shifted the shoreline.