firestone
Fire"stone` (; 110), n. Etym: [AS. f flint; f fire + stan stone.] 1. Iron pyrites, formerly used for striking fire; also, a flint. 2. A stone which will bear the heat of a furnace without injury; -- especially applied to the sandstone at the top of the upper greensand in the south of England, used for lining kilns and furnaces. Ure.