The elusive Lake Superior agate. Rockhounds scour Lake Superior’s shoreline for these rare banded beauties—from the western reaches of the Keweenaw Peninsula to the U.P.’s easternmost Whitefish Point.

Yooperlites are rocks that fluoresce under UV light. The best time to search for Yooperlites is after a storm, when waves may have unearthed new rocks along the shores of Lake Superior. Rock hunters ...