turquoise vs opaque gem

turquoise and opaque gem both are nouns.

Word	Noun	Adjective	Verb	Adverb
turquoise	Yes	No	No	No
opaque gem	Yes	No	No	No

As nouns, opaque gem is a hypernym of turquoise; that is, opaque gem is a word with a broader meaning than turquoise:

turquoise: a blue to grey green mineral consisting of copper aluminum phosphate
opaque gem: a gemstone that is opaque

Other hypernyms of turquoise include mineral.

turquoise (noun)	opaque gem (noun)
a shade of blue tinged with green	a gemstone that is opaque
a blue to grey green mineral consisting of copper aluminum phosphate