consisting of or having the hardness of adamant
having the hardness of a diamond
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"
"an intransigent conservative opposed to every liberal tendency"
Made of adamant, or having the qualities of adamant; incapable of being broken, dissolved, or penetrated.