hardness vs unfeelingness

hardness and unfeelingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
hardness	Yes	No	No	No
unfeelingness	Yes	No	No	No

As nouns, hardness and unfeelingness are synonyms defined as:

hardness and unfeelingness: devoid of passion or feeling; hardheartedness

Other synonyms of hardness include callosity, callousness, insensibility.

hardness (noun)	unfeelingness (noun)
a quality of water that contains dissolved mineral salts that prevent soap from lathering	devoid of passion or feeling; hardheartedness
the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale
the quality of being difficult to do
devoid of passion or feeling; hardheartedness
excessive sternness