New home. Hate the tiny shelves. Want to remove them, put a normal mantle in, and a TV above.
If you're putting a mantle in there you've got some major work ahead of you, and this is just a minor step. Taking those out is just a matter of chipping away the mortar around them with a suitable tool and cracking them loose. I doubt they have any additional fastening beyond the same mortar that holds the rest of the stone in place.