I have never drilled through rocks before and I am wondering how different
it will be compared to drilling through solid concrete. I suspect it may be
harder?

I have an exterior wall that is a 12" thick concrete block wall (8" block
with a layer of 4" block), and on the outside of this is a layer of
rock/stone face like this:

http://i173.photobucket.com/albums/w...ckfacewall.jpg

I want to add a hose bib on that wall. I have access from the inside and a
copper pipe is near by that I can split off and run a 1/2" copper pipe
there. I have a rotary hammer with concrete bits and I can chew through the
12" concrete block like butter, but I am not so sure about this rock...I
don't want to end up pushing a piece of rock completely out, and if I can
drill into it I don't know how clean the hole will be, will I end up
cracking it into two?

I don't have a spare piece of rock or I would try to drill it just to see.

Thanks in advance,

MC