nouns
the muscle tone of healthy tissue
"his muscular firmness"
the trait of being resolute
"his resoluteness carried him through the battle"; "it was his unshakeable resolution to finish the work"
the property of being unyielding to the touch
is a type of (narrower)
the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale
the quality of being steady or securely and immovably fixed in place