What did he find from the rocks? Probably something more useful than debating the blueness of the sky (a personal favorite of humans). The Doctor stared up indignantly at Jamie. "I found plenty, and I'm sure I could find out a lot more if I could take one back to the TARDIS for further study."

He's just...not going to mention that everything he's discovered so far is by sheer absence: he's learning what the rock Isn't made of because he can't identify any of the substances and it's going very much back to basics by looking and feeling it. Of course Jamie might not quite see it that way. The Doctor does have to agree with one thing: the priests are probably their best direction to go with.

"Good point," the Doctor says, willing to drop discussions about rocks for priests. "Going to be interesting to see what the rituals look like."