calcite vs Mexican onyx

calcite and Mexican onyx both are nouns.

Word	Noun	Adjective	Verb	Adverb
calcite	Yes	No	No	No
Mexican onyx	Yes	No	No	No

As nouns, Mexican onyx is a hyponym of calcite; that is, Mexican onyx is a word with a more specific, narrower meaning than calcite:

calcite: a common mineral consisting of crystallized calcium carbonate; a major constituent of limestone
Mexican onyx: a hard compact kind of calcite

Other hyponyms of calcite include alabaster, onyx marble, oriental alabaster, chalk, Iceland spar.

calcite (noun)	Mexican onyx (noun)
a common mineral consisting of crystallized calcium carbonate; a major constituent of limestone	a hard compact kind of calcite