Buy a medium to high quality glass front and insulate the sides and top with high-temperature stuffing wool. This will prevent most of the smoke when lighting a fire to excape and mark the stone. The high-temp stuffing wool is white and is safe over 1500 degrees. The middle of the road stuff is yellow and begins to melt over 800 degrees.
Also, think about getting a fireplace rug to protect whatever is in front of the fireplace. If you have a rug, or hardwood in the room, hot coals can spit out and mark (burn) a rug or floor. A small 3x5 rug, perferrably with a pattern to hide small burns, can be placed in front of the fireplace to protect the more permanent floor covering. This also protects the floor from dirt when bringing in wood. When the fireplace is in a basement with a cement floor, then there is no need for a rug.