All about "Yooperlite".

 "Yooperlite" is a trade name used to refer to fluorescent pebbles found along the beaches of Lake Superior in Michigan. These unique rocks are a type of syenite containing the mineral sodalite, which exhibits a distinct fluorescence when exposed to ultraviolet (UV) light. 

Yooperlite video

The term "Yooperlite" pays homage to the residents of Michigan's Upper Peninsula, who are colloquially known as "Yoopers." Using a UV fluorescent light to illuminate these rocks reveals their captivating glow, making them a popular find among rockhounds and collectors.