Michigan rock hunting is a passion unlike anywhere on Earth, because we have the best darn beaches anywhere on Earth. Here is just about everything you need to get started, from where to look to what to look for. Grab a bucket, the sunblock and keep your eyes on the prize.
We all have that one rock. Our favorite rock. The rock. We remember exactly where we found it, who we were with, the weather—everything. My rock is a Leland Blue the color of a robin’s egg and about the size of my fist. I found it on a sunny afternoon in June 2016. The air was 80-something degrees and Lake Michigan was that stop-and-stare Caribbean blue. It was sitting in the sand on Van’s Beach about 10 feet from the water’s edge. I held on to it so tightly on the walk home, that the round outline was imprinted on my palm.
Perhaps no one understands the lure of the rock better than Traverse City’s Kevin Gauthier. When Kevin was nine, he spent the summer lying on his surfboard face-down in Lake Leelanau looking for Petoskey stones. He filled shoe boxes with his treasures, and pretty soon, his entire closet was stacked high with heavy, rock-filled shoe boxes.
Years later, Kevin turned down a promotion at his job in Chicago and instead came back home to start a rock shop. It’s a decision he doesn’t regret 21 years later. At Korner Gem, tucked across the street from West Grand Traverse Bay and Greilickville Harbor Park, you’ll find thousands of stones in every color—and Kevin grinning as he polishes a Petoskey.
Michigan is home to the most varieties of stones in the entire world, Kevin says. Glaciers covered almost 200 million acres when they formed and acted like a giant conveyor belt bringing rocks south to what is now Michigan.
Kevin gives us a lesson on Northern Michigan’s most iconic stones…
Photo by Marcelina Clark
Photo by Kelsie Sullivan
PETOSKEY STONES
Michigan was once covered by seas that were home to a variety of corals, including Hexagonaria percarinata. Petoskey stones were created about 400 million years ago. They are deposits from the ancient coral, which became embedded in limestone bedrock. During the Ice Age, glaciers broke up the bedrock, and the ice’s movement smoothed the chunks of fossilized coral.
Did You Know: Petoskey stones aren’t only found at the beach. They are scattered everywhere across the Lower Peninsula. You can even find them in parking lots and your own backyard. However, there are no Petoskey stones north of Harbor Springs. The northern rim of the coral reef was there, and glaciers pushed the stones south. Wanna be a Petoskey pro + learn how to polish them at home?
LELAND BLUE + MORE…
These brilliant blue, green and purple treasures aren’t actually stones. They’re slag, a byproduct of Michigan’s historic smelting industry. When raw ore is heated, the iron ore is separated from impurities. After the impurities cool, the result is slag. Slag can be found in Frankfort, Cadillac, Elk Rapids, Fayette, Marquette— anywhere smelting was done. When the smelting industry ended in Leland, heaps of slag were dumped in Lake Michigan. Because slag is still commonly found in the area, it’s become known as Leland Blue.
Fun Fact: Slag is found in a variety of colors like Frankfort Green. Why? Some people think it’s due to the type of wood used to fuel the smelting furnace, but the same type of wood found in Frankfort back in the 1800s would likely have been found in Leland, too. Kevin’s theory: “I think they were experimenting with increasing and decreasing oxygen levels to create a higher-quality steel since loggers needed hard and springy saws.”
A pudding stone // Photo by Debra Stephens
PUDDING STONES
Glaciers brought these conglomerates (which resemble a Christmas pudding) south from Thessalon, Canada. The stone contains rounded pebbles of red jasper, black chert and white quartzite “cemented together” by quartz. You’ll find pudding stones on Drummond Island and along Michigan’s eastern shore (you can find small ones in Lake Michigan, but they’re very rare). Large pudding stone boulders have been found near Clare.
Whoa. The pebbles in pudding stones date back 2.4 billion years. The pebbles were smoothed and rounded by an ancient river. When glaciers compressed the river bottom, the pebbles were “glued” together.
Mighty Lake Superior // Photo by Thomas Bos
LAKE SUPERIOR AGATES
These semi-precious gemstones range from pea-sized to 20-plus pounds and occur in a variety of colors including brown, white, red, gray, pink, black and yellow. Lake Superior agates are the oldest on earth. They formed 1.2 billion years ago during lava eruptions. The next oldest are the Montana moss agates, a mere 370 million years old.
Agate Trivia
Nickname: “Lakers”
Best time to look: Right after a storm
What town’s beaches are prized for agates?
FAVORITE FOSSILS
This petrified coral is also known as Charlevoix Stone and is a cousin of the Petoskey. It actually resembles a “miniature” Petoskey stone, because the coral had a smaller exoskeleton chamber. (Think of a Petoskey stone as a bundle of pencils and the Charlevoix stone as pencil tips.)
Cool! Charlevoix Stones are rarer than Petoskeys. But it’s more common to see them at popular beaches, because most of the Petoskeys have already been picked up.
Want more rock-hunting tips, guides, how-to's and more? We've got it!
7 Things to Know About Michigan Rock Hunting
- Michigan is home to the most varieties of stones in the entire world, Kevin says. Glaciers covered almost 200 million acres when they formed and acted like a giant conveyor belt bringing rocks south to what is now Michigan.
- The coral that formed Petoskey stones (Hexagonaria percarinata) went extinct before dinosaurs were even born. So, when you find a Petoskey stone, you’ve found an animal that’s older than a dinosaur!
- Northern Canada is home to several large diamond deposits, and glaciers snuck some south to Michigan. Diamonds are found within a 200-mile swath that runs from Iowa to Ohio. The largest have been found near Milwaukee—including one that was more than 21 carats. A 10-carat diamond was found near Dowagiac, Michigan—which may be the largest found in the state, says Bruce Mueller of C&M Rock Shop in Honor.
- Fulgurites are formed when lightning strikes sand. The heat liquifies the sand into a glass cone. Your best chance of finding a fulgurite is to go to a beach or high sandy area during a storm—do not get out of your car—and watch for lightning strikes. Or walk the beach after a storm. (Not to be confused with lightning stone, a concretion found near Saugatuck that has white calcite running through it, like lightning strikes.)
- Meteorites can be found in Michigan. Where? Well, that’s anybody’s guess, Kevin says.
- Michigan law states that an individual cannot remove more than 25 pounds per year of any rock, mineral (exclusive of any gold bearing material) or invertebrate fossil from state-owned land for personal or non-commercial hobby use.
- It is illegal under federal law to remove stones from a National Lakeshore.
Our state stone, the Petoskey. // Photo by Gail Snable
10 Best Rock Hunting Beaches in Northern Michigan
It was a very close call, but these are our readers’ top 10 favorite rockhounding haunts in our 2019 Red Hot Best of Northern Michigan contest. If you go, good luck, and save some for the rest of us!
- Van’s Beach, Leland
- Petoskey State Park
- Point Betsie Lighthouse Beach, Frankfort
- Empire Beach
- Mission Point Lighthouse, Old Mission Peninsula
- Barnes Park, Antrim County
- Peterson Park, Northport
- Christmas Cove, Northport
- Wilderness State Park, Carp Lake
- Frankfort Public Beach
Rockhounds, check out “Lake Michigan Rock Picker’s Guide,” “Lake Superior Rock Picker’s Guide” and “Lake Huron Rock Picker’s Guide” co-authored by Kevin Gauthier and Bruce Mueller for more information about our state’s coolest stones.