A new type of rock has been found in Michigan's Upper Peninsula, WPBN/WGTU reports. Dubbed "yooperlites" by their discoverer Erik Rintamaki, the pebbles look unremarkable in plain daylight—but hold them under an ultraviolet lamp, and they glow orange.

Rintamaki, a self-described "rock hound," made the discovery while scouring the shores of Lake Superior with a UV light last year. Some of the rocks he came upon lit up with brilliant gold flecks when illuminated. He took some home and started selling them under the name yooperlites, a play off Yoopers, the name residents of Michigan's Upper Peninsula give themselves ("U.P.-ers").

One of his buyers was the nearby Michigan Tech University. After testing the rocks, the university's geologists reached out to Rintamaki with the results: The yooperlites were found to be syenite rocks that contain sodalite, a fluorescent mineral that had never before been identified in Michigan by scientists. The sodalite is what gives the yooperlites their otherworldly glow.

Rintamaki has since succeeded in turning his discovery into a small business. He now sells boxes of yooperlites for $32 a pound and gives guided rock-hunting tours around Lake Superior for $50 per person. You can get in touch with Rintamaki about his tours or his rock business through the Yooperlites Facebook page.

[h/t WPBN/WGTU]

All images courtesy of Erik Rintamaki.