Forget Petoskey stones, there's another unique rock you should be keeping your eye out for the next time you head up north.
Walking along the beach, you might see this rock and think it's perfectly average. But when you shine a UV light on it, it glows.
Geologists say it's a new type of rock in Michigan.
Erik Rintamaki has been a self-proclaimed 'rock-hound' his whole life.
But last year, he decided to hit the beach at night with a UV light, and came home with his first yooperlites.
"I actually sold a few at Michigan Tech University, and they sent them out for testing and they contacted me through emails and told me I probably had something new that had never been found in Michigan before and I ended up being published in the Mineral News in 2018 for that discovery," said Erik Rintamaki, who discovered the yooperlites.
Yooperlite is the name Rintamaki came up with, but geologists say they are syenite rocks rich in fluorescent sodalite.
"So, what that is, is just a beach granite or basalt that has a fluorescent mineral in it called sodalite that they believe was brought down from Canada by glaciers," Rintamaki said.
Rintamaki isn't the first person to discover these glowing rocks, but was the first to bring them to geologists who verified there is sodalite in Michigan.
He has now collected dozens of yooperlites and he sells them for $32 a pound.
"My business has blown up," he said.
The glowing rocks can be found mostly on Lake Superior between Whitefish Point and Grand Marais and on the Keewenaw Peninsula.
Rintamaki routinely leads guided tours on how to find these rocks.
Two such tours are set to take place at Muskallonge Lake State Park in Newberry Saturday and Sunday.