I have a new KraftMaid cabinet (to be used as a bookcase) that I want to
mount on a stone wall (actually the chimney in an old New England center
chimney home). The surface is very irregular, and I am assuming the stone
is granite. It's been painted so many times, it's not easy to tell which
is stone and which is mortar.

My intent is to mount a board to the wall with masonry anchors, and then
mount the cabinet to that. First problem is that most local hardware
stores (including the HD) only have light duty anchors, and where I found
mid or heavy duty, I couldn't find anyone who could explain the different
types or make a useful recommendation.

In addition, the first hole I drilled hit a void in the mortar, and so
seems useless for any anchor. The next hole I tried didn't go anywhere,
although I was using a very old masonry bit.

Will a new masonry bit make a dent in the stone, or do I absolutely need
to find the mortar or rent or borrow a hammer drill?