Real limestone fireplaces
Fireplaces can of course be made from many materials, and there are companies that offer every option. Historically of coarse they were most often made from brick; stone; or some other masonry or clay based substance. This is because those materials are resistant to heat and because they were used for all aspects of dwelling construction.
Stone of course was always used for the grander buildings, as it was incredibly resilient to the elements, (and to attack from invaders) it’s not unusual to find vast castle walls in an otherwise ruined castle, with stone fireplaces still intact, built into those walls. It’s not hard to imagine the Laird standing in the great hall or dining room that contained these stone fireplaces: Piled high in winter with a roaring fire of big logs, and maybe a suckling pig roasting on a spit over the flames.
A stone fireplace was even then, the centre piece of a room, not least because castles were invariably of course, freezing cold! They built their stone fireplace big in those days, so you could heat more people, and burn bigger ‘piles’ of logs. This truly was the only source of heat, and it must have been bitterly cold in a chamber without a fire.
That’s of course why you find stone fireplaces in most castle rooms. Smaller perhaps than those in the great halls, but even a bed chamber needed some source of heat to fend of hyperthermia to the old toes should they peep from under the bed covers.