adamantine (
http://definr.com/adamantine)
adj 1: consisting of or having the hardness of adamant
2: having the hardness of a diamond
3: 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" [syn:
adamant,
inexorable,
intransigent]