The Doctor taps the boulder. Really, she should have a sniff herself, but...right, yeah. The dead thing. She might not even have a working olfactory system, which is rather unfortunate. "They're alien rocks, Karis. A whole new world, in a whole new dimension!"

As for metals, he's not sure. Possibly? He thinks he detected iron, if iron fell face first into some helium and somehow popped out...whatever's actually in this rock. For once his usually accurate sense of taste and smell aren't helping him identify this rock and he's really only established that it's white, big, heavy and covered in little dimples. Pits, almost. Almost like pumice. The Doctor looks up at Karis, glad to see she's behaving herself with that boot, because he might've accidentally put himself within boot radius when he stopped at the rock.

Whew. The Doctor might be inching over to put the boulder between him and Karis in case that boot changes its mind. He also motions her to take a much closer look, as if they're just on a sightseeing trip.

"I haven't the faintest about what's in it," the Doctor admits. "Difficult to say what's considered useful in this universe, at least just from a few minutes out here."