Chances are, the only way to find out how solid they are is to smack ‘em with something and see what happens. Teller suggested a large number of bullet-shaped tungsten objects, embedded in a sort of net. It would be launched wadded up, then deployed opened up wide, and sent head-on into the interloper rock. Most of the energy to slice-and-dice would be from the rock itself.
I would think a spear that penetrated deep in, with the energy breaking it from inside.