My wife has a small rectangular slab about 12" x 16" with a stained glass design glued to it. A couple of small pieces (approx. 1/2 inch by 3")have broken off. These pieces fit right up tight to the stained glass. It would be difficult to reattach them with concrete as the edge would no longer be smooth. Can I use epoxy to reattach them? If not what should I use? Thanks, in advance, for your help.

Post a picture.

A thin epoxy should work best. Maybe a gel Superglue, depending on how porous the concrete is.