I took a week off to relax before starting my new job, and the yellow tiles on the hearth with the chipped corner were getting on my nerves. So, I took a mortar chisel to them and they were gone in a few hours.
Replaced them with some McNear Red Hills brick.
Couldn't find white mortar, so I had to settle for grey, but it worked out okay since some of the other mortar around the fireplace has greyed over the years.
Note: Splitting bricks in half with a brick set is easy. Cutting off corners is not. I broke so many bricks that I almost had to go back to the rock & soil yard for more.
Note: A 60 pound bag of dry mortar does not go as far as you think it would. I ran out before I laid the last few bricks.