volcanic rock vs dacite

volcanic rock and dacite both are nouns.

Word	Noun	Adjective	Verb	Adverb
volcanic rock	Yes	No	No	No
dacite	Yes	No	No	No

As nouns, dacite is a hyponym of volcanic rock; that is, dacite is a word with a more specific, narrower meaning than volcanic rock:

volcanic rock: extrusive igneous rock solidified near or on the surface of the Earth
dacite: a grey volcanic rock containing plagioclase and quartz and other crystalline minerals

Other hyponyms of volcanic rock include agglomerate, amygdaloid, basalt, volcanic glass, lava, tufa, tuff.

volcanic rock (noun)	dacite (noun)
extrusive igneous rock solidified near or on the surface of the Earth	a grey volcanic rock containing plagioclase and quartz and other crystalline minerals