Yeah, shining a UV light on marbles can be all kinds of fun, and sometimes it can even help with ID. JABO made a Classic called a JABO Ghost - dullest marble ever until you put UV on it, then it lit up in a variety of colors.
But as far as marbles go, a wise collector once told me, "if you need UV light or magnification to see it, it may as well not be there". lol