I found this pebble (it is pretty small) on a beach just north of Chicago. It is a slightly translucent stone that wouldn't catch a second glance apart from the fact that it glows bright orange under SW UV. I haven't the faintest idea what it is. I've gone back to the beach to look for more, and I did find one other small rock like it, plus a fair amount of what is probably slag glass that also glows orange. Let me know if you have any ideas what it could be.