amethyst vs chromatic

amethyst is a noun but chromatic is not a noun.

Word	Noun	Adjective	Verb	Adverb
amethyst	Yes	Yes	No	No
chromatic	No	Yes	No	No

amethyst (noun)	chromatic (noun)
a transparent purple variety of quartz; used as a gemstone

amethyst (adjective)	chromatic (adjective)
of a moderate purple color	being or having or characterized by hue
	based on a scale consisting of 12 semitones
	able to refract light without spectral color separation