feldspar vs plagioclase

feldspar and plagioclase both are nouns.

Word	Noun	Adjective	Verb	Adverb
feldspar	Yes	No	No	No
plagioclase	Yes	No	No	No

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

feldspar: any of a group of hard crystalline minerals that consist of aluminum silicates of potassium or sodium or calcium or barium
plagioclase: any of a series of triclinic feldspars that form rocks

Other hyponyms of feldspar include orthoclase, oligoclase, moonstone.

feldspar (noun)	plagioclase (noun)
any of a group of hard crystalline minerals that consist of aluminum silicates of potassium or sodium or calcium or barium	any of a series of triclinic feldspars that form rocks