[adj] not capable of being swayed or diverted from a course; unsusceptible to persuasion; "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 tendancy"
[adj] having the hardness of a diamond
[adj] consisting of or having the hardness of adamant