spinel vs ruby spinel

spinel and ruby spinel both are nouns.

Word	Noun	Adjective	Verb	Adverb
spinel	Yes	No	No	No
ruby spinel	Yes	No	No	No

As nouns, ruby spinel is a hyponym of spinel; that is, ruby spinel is a word with a more specific, narrower meaning than spinel:

spinel: a hard glassy mineral consisting of an oxide of magnesium and aluminum; occurs in various colors that are used as gemstones
ruby spinel: a spinel used as a gemstone (usually dark red)

Other hyponyms of spinel include spinel ruby, ceylonite, pleonaste.

spinel (noun)	ruby spinel (noun)
a hard glassy mineral consisting of an oxide of magnesium and aluminum; occurs in various colors that are used as gemstones	a spinel used as a gemstone (usually dark red)