>>2936727
Is his going to be outside or inside? If outside, probably want to go with granite and make the hole a good 5% bigger than it needs to be and put a flexible adhesive to mount it. Also make sure the iron is painted or the rust expanding will split the rock.

>what to use
Again depends, Use a core bit, use it wet and go extremely slowly, always pulling the bit out and dipping it in water. Don't use oil.