Petoskey Stone Hunting: A Complete Beginner Guide

What Is a Petoskey Stone?

A Petoskey stone is a piece of fossilized coral — specifically the colonial coral Hexagonaria percarinata — that lived in a warm, shallow sea covering Michigan roughly 350 million years ago. When wet, the stone reveals a pattern of interlocking hexagonal cells, each the fossilized skeleton of an individual coral polyp. When dry, the pattern fades to a subtle grey-brown that makes them hard to spot on a pebble-covered beach.

Michigan designated the Petoskey stone as the official state stone in 1965. Finding one is a rite of passage for anyone who spends time on the Lake Michigan and Little Traverse Bay shorelines — and the search itself, head down and shuffling slowly along the waterline, is oddly meditative.

Where to Hunt: The Best Beaches

Petoskey State Park — Magnus Park Beach and Petoskey State Park beach on Little Traverse Bay are the most reliable locations in the state. The stones are tumbled smooth by wave action and are concentrated at the waterline and in the shallows. Fisherman's Island State Park south of Charlevoix is another premier location and receives fewer visitors. Traverse City State Park beach has them, though they are rarer. The shoreline between Northport and Leland along M-22 offers good access with light foot traffic.

How to Identify Them Wet vs. Dry

The key is water. Carry a small water bottle and wet any promising grey stone. A Petoskey stone wet will show the honeycomb pattern clearly — concentric rings of six-sided cells radiating from a center point. Common confusion stones include: ordinary limestone (no pattern), dolomite (similar color, no coral structure), and slag glass (artificial, too smooth). Petoskey stones have a matte finish when dry and a slight translucence when wet. Size ranges from marble-sized to grapefruit-sized; larger ones are rarer and more impressive.

When to Hunt

Spring and fall are better than summer for two reasons: fewer other people hunting them, and wave action from winter storms stirs and deposits fresh stones on the beach. The best time of any day is just after a storm when the water has sorted and concentrated stones at the high-water line. Early morning before other walkers is also productive. Summer is still worthwhile — just work the shallow water rather than the dry beach, where competition is highest.

What to Do With Your Petoskey Stones

Raw Petoskey stones are beautiful when wet and subtle when dry. Tumbling in a rock tumbler for 2-3 weeks produces a polished stone that holds the pattern visibly without water — this is what most of the commercial Petoskey stone jewelry uses. Lapidary shops in Petoskey and Traverse City can cut and polish stones for you. Many people simply collect them in a bowl of water or mineral oil to keep the pattern visible. Drilling for pendants requires a diamond-tipped bit and patience.

Rules and Ethics

In Michigan state parks, collecting rocks (including Petoskey stones) is limited to a small quantity for personal use — not commercial collection. Check the specific park's regulations. On federal lands (National Lakeshore), collection of any natural objects including rocks is prohibited. On private beaches or open Lake Michigan public shoreline below the high-water mark, collection is generally permitted in reasonable quantities. Take what you can genuinely use and leave the rest for the next person to discover.

The Culture of the Stone

Petoskey stone hunting has a whole subculture around it — Facebook groups where hunters post their finds, local festivals celebrating the stone, jewelry makers and artists who build entire careers around it. The annual Petoskey events calendar includes stone-themed events that connect visitors with local lapidaries and collectors. It is a small and enthusiastic world, and finding your first nice specimen has a way of making you want to join it.