hardness vs callousness

hardness and callousness both are nouns.

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

As nouns, hardness and callousness are synonyms defined as:

Other synonyms of hardness include callosity, insensibility, unfeelingness.

hardness (noun)	callousness (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