I don't know that I'd try an unglazed tile as a pizza stone. That just seems fraught with peril, to me, plus there's the issue of getting them out of the oven. You'd have to wait forever for them to cool so you didn't get burned when you removed the stone. And if they're prone to cracking, I think I'll just stick with a pizza stone that's made for that purpose. It might be more expensive, but at least I'd have a warranty on it if it cracked!