humate vs brown coal

humate and brown coal both are nouns.

Word	Noun	Adjective	Verb	Adverb
humate	Yes	No	No	No
brown coal	Yes	No	No	No

As nouns, brown coal is a hyponym of humate; that is, brown coal is a word with a more specific, narrower meaning than humate:

Other hyponyms of humate include peat, lignite, wood coal, humic shale.

humate (noun)	brown coal (noun)
material that is high in humic acids	intermediate between peat and bituminous coal