sandstone vs brownstone

sandstone and brownstone both are nouns.

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

As nouns, brownstone is a hyponym of sandstone; that is, brownstone 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.)
brownstone: a reddish brown sandstone; used in buildings

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

sandstone (noun)	brownstone (noun)
a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.)	a row house built of brownstone; reddish brown in color
	a reddish brown sandstone; used in buildings