Add Yahoo as a preferred source to see more of our stories on Google. Most people do their rock hunting during the day, but you can't find "Yooperlites" until the sun goes down. Yooperlites are rocks ...

Most people do their rock hunting during the day, but you can't find "Yooperlites" until the sun goes down. Yooperlites are rocks that fluoresce in the dark under ultraviolet light. They became known ...