Fragile?

Mike: Dad can I take my sharks tooth to school with me?
Me: I don't know Mike, why do you want to take it with you?
Mike: You're right I probably shouldn't it's fragile.
Me: It's not really that fragile bud.
Mike: Well, it'll break if you hit it with a sledge hammer.
Me: That doesn't make it fragile Mike, the sidewalk would break if you hit it with a sledge hammer.
Mike: Really? Next time we're walking on the side walk can I take a sledge hammer...
Me: Umm, No, you can't.