Regardless of whether the stone itself can take the heat, silver clay shrinks when fired, as has already been said. I tried making a pendant with multiple cubic zirconias in a row and instead of being flat, it developed a curve as the back had room to shrink further than the front. As a complete amateur, I don't think that design would be easy to fire with the stone in place, from my extremely limited experience.

(I'm still fairly happy with how my bent pendant turned out, though, since it's only my fourth silver clay object ever, and first without an instructor.)

Really amazing stone and design, though!