adamantine

adjectives

consisting of or having the hardness of adamant
adamantine
pertains to
adamant
having the hardness of a diamond
adamantine
is similar to
resisting weight or pressure
hard
impervious to pleas, persuasion, requests, reason
"he is adamant in his refusal to change his mind"; "Cynthia was inexorable; she would have none of him"- W.Churchill; "an intransigent conservative opposed to every liberal tendency"
adamant, adamantine, inexorable, intransigent