[@Katakon] A prism's really just a shape. Most any transparent or highly transcluent gem could be a prism. If you wanna go for that as the name, go for it, but the gem itself should be, well, fluorite. At least that's what I think. The ultimate word is Akaya's and Kronshi's, of course.

And a little fyi as the local gem geek, I think you mean fluoride/optical glass? That's...Usually what's used. Fluorite is very rarely clear. It's usually a mix of green, blue, and purple. ^ ^" I'