Rintamaki self-named the rocks “Yooperlites” in honor of the endearing nickname “Yooper” for people who live in Michigan’s Upper Peninsula.

The Yooperlites were investigated by both Michigan Tech University and the University of Saskatchewan. They determined the rocks are “syenite clasts containing fluorescent sodalite.” To break this down, the rock is made up of fragments of coarse-grained igneous rocks, with a similar composition to granite. What makes these rocks special is the inclusion of fluorescent sodalite.