sandstone vs firestone

sandstone and firestone both are nouns.

Word	Noun	Adjective	Verb	Adverb
sandstone	Yes	No	No	No
firestone	Yes	No	No	No

As nouns, firestone is a hyponym of sandstone; that is, firestone is a word with a more specific, narrower meaning than sandstone:

sandstone: a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.)
firestone: a sandstone that withstands intense heat; used to line fireplaces and furnaces and kilns

Other hyponyms of sandstone include holystone, grit, gritrock, gritstone, brownstone, bluestone, greensand, siltstone.

sandstone (noun)	firestone (noun)
a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.)	a sandstone that withstands intense heat; used to line fireplaces and furnaces and kilns
	a piece of flint that is struck to light a fire