sapphire vs corundum

sapphire and corundum both are nouns.

Word	Noun	Adjective	Verb	Adverb
sapphire	Yes	Yes	No	No
corundum	Yes	No	No	No

As nouns, corundum is a hypernym of sapphire; that is, corundum is a word with a broader meaning than sapphire:

sapphire: a precious transparent stone of rich blue corundum valued as a gemstone
corundum: very hard mineral used as an abrasive

Other hypernyms of sapphire include corundom, transparent gem.

sapphire (noun)	corundum (noun)
a light shade of blue	very hard mineral used as an abrasive
a transparent piece of sapphire that has been cut and polished and is valued as a precious gem
a precious transparent stone of rich blue corundum valued as a gemstone

sapphire (adjective)	corundum (adjective)
of something having the color of a blue sapphire