hardness vs ruggedness

hardness and ruggedness both are nouns.

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

As nouns, hardness and ruggedness are synonyms defined as:

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