Ulexite

Years ago I was perusing the shelves and bins at Appalachian Rock Shop when I came across an oddity.  There was a chunk of a clear-ish, somewhat milky mineral that when placed over top of something, particularly noticeable on printed words, seemed to bring the image to the surface of the crystal.  The owner told me that it was ulexite, a natural fiber optic.  I was intrigued and a bit giddy, so I bought a couple of pieces and took them home to impress my friends.  Of course my friends weren't impressed ("It's just a rock."), but I was, and still am.