Overview
Michigan's beaches and old copper country make it one of the best rock-hunting states in the Midwest. The Great Lakes shorelines yield fossil Petoskey stones and banded agates, while the Keweenaw Peninsula is famous for native copper and the state gem, greenstone.
This guide covers common and iconic Michigan rocks and minerals — how to recognize them by color, pattern, and form. Photograph your specimen from a couple of angles and use the app to help confirm what you have found.
Key Species to Know
Petoskey Stone
Petoskey stone
Michigan's state stone — fossilized colonial coral showing a honeycomb of six-sided cells, most striking when wet or polished. Found along northern Lake Michigan beaches.
Lake Superior Agate
Agate
A banded, waxy-lustered quartz in reds, oranges, and whites, tumbled smooth by the lakes. Its iron-rich color bands set it apart from plain beach pebbles.
Native Copper
Copper
Reddish, metallic copper metal in its natural form, sometimes in branching or nugget shapes, weathering to green. The Keweenaw Peninsula was mined for it for over a century.
Greenstone (Chlorastrolite)
Chlorastrolite
Michigan's state gem — small green pebbles with a distinctive turtleback, segmented pattern, weathered from Keweenaw basalt. Rare and much sought after.
Datolite
Datolite
A porcelain-like nodule mineral in white, pink, or tan, found in the copper country's basalt, sometimes with copper inclusions. Prized by local collectors.
Quartz
Quartz
Common as clear or white pebbles and crystals, and as the material of the agates and jaspers on Michigan's beaches. Hard, glassy, with curved fractures.
Seasonal Guide
- Hunt beaches after storms and in spring, when waves expose fresh gravel.
- Wet every likely stone — Petoskey stones and agates show their pattern and color best when wet.
- Bright sun low on the water helps agates glow; a spray bottle saves a lot of lake-dipping.
Safety Reminder
This is an identification guide only. Collecting is prohibited in national parks such as Isle Royale, and limited on some state land — know the rules for your beach. Never enter old copper-mine workings, and respect private shoreline.
Identify it instantly
Found something and not sure what it is? Point your camera with Spotter and get a species identification in seconds — with detailed reference info and species notes.