u/PorcelainFD

Found at the edge of Lake Superior in Duluth, Minnesota. When dry, the rectangular bits are shiny in direct sunlight. Only a very tiny bit glows yellowish-white in UV light - that part is as wide as uncooked spaghetti and less than a centimeter in length. It’s indistinguishable (to me) in natural sunlight. I assume some type of granitoid.