[ On the outside: he keeps his surprise fairly mild, then closes his eyes with an exasperated sort of laugh at the idea. Maybe the man is just a supreme eccentric? Things are starting to shape up to look like that, from his perspective. He gestures with a hand between them both. ]

While we might learn something from trying that.... we don't know the nature of these stones. They could have a spell cast on them that activates under certain conditions or under duress. I'd hate for harm to come to one or both of us as a result.

[ a beat, and then, more earnest: ]

You aren't afraid of what may happen to you, if it breaks...?