There is fireclay [1], and I have fireplace with several bricks made from it. When fired in the evening for 2-3h, will keep warm until morning. [1] https://en.

There is fireclay [1], and I have fireplace with several bricks made from it. When fired in the evening for 2-3h, will keep warm until morning. [1] https://en.wikipedia.org/wiki/Fire_clay https://en.wikipedia.org/wiki/Fire_clay