What is 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 called?

firestone — 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. (Webster's 1913.)