EGLE rockhound offers tips to find elusive, glowing ‘Yooperlites®’

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June 05, 2023

With summer vacation season here, thousands of people will head to Michigan's Upper Peninsula for some rest and relaxation. For many people, that time will include rock hunting – especially for the elusive Yooperlite®, a fluorescent rock that glows "in the dark" under ultraviolet light. The rock first became known when a U.P. resident discovered them in 2017.

Rob Wolfe, an environmental quality analyst in the Michigan Department of Environment, Great Lakes and Energy's Marquette District Office, has been a rockhound in Michigan's Upper Peninsula for 50 years.

Rob Wolfe, of EGLE's Marquette District Office, examines a sedimentary rock along Lake Superior.

In normal light, a Yooperlite® looks like granite. Sodalite replaces quartz, so the larger the mineral size, the brighter the shine, says Wolfe.

There are some five classes of Yooperlites®, Wolfe adds:

Sodalite syenite (Yooperlite®) on display at the A.E. Seaman Mineral Museum in Houghton, Mich. Courtesy of A. E. Seaman Mineral Museum.

He has found too many Yooperlites® to number and has given most away to promote the rock hunting activity. "The largest was about the size of a baseball, but I would say based on the size of gravel where I search, most are the size of a ‘pinky nail’ to thumbnail length," Wolfe notes. "I have seen cantaloupe-sized ones found in Houghton County or from divers. There is a limit to how much one can take from public beaches."

Wolfe offers the following tips to find this mysterious rock in the Upper Peninsula:

If you are not successful at finding Yooperlites®, you can still see them, as they are now on display at the A.E. Seaman Mineral Museum at Michigan Tech University in Houghton. The museum is open from 9 a.m. to 5 p.m. Monday through Saturday.

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