I just read an opinion piece in the Wall Street Journal that has the headline
We’re Governed by Callous Children
In its literal sense the adjective callous is used to describe parts of the skin that are hardened by constant friction or pressure. Used figuratively it refers to insensitive behavior, or hardness of the mind.
Here are some more examples from the web:
Why are people so callous when you need help?
Rude, Callous, Indifferent Customer Service People
SSPCA hunts ‘callous person’ responsible for animal cruelty case
A calloused heart is like a stone.
they brought it on themselves by their selfish and calloused behavior toward the poor.
A variant spelling of callous is callus. This spelling is usually seen in connection with body parts:
Home Remedies for Dry Callused Feet
Frustrated with Crepey, Dry, Callused Hands?
Sage Bath For Hard & Callused Skin
Used literally, the spellings are interchangeable. A foot may be either calloused or callused.
When using the adjective in a figurative sense, however, stick to callous and its forms: a callous person, calloused behavior.
Actually, at least according to Merriam-Webster, there is no adjective form of callus, only of callous, for whatever that’s worth. But apparently Paul Brian–Common Errors in English Usage–also says to use callused for body parts.