Source : Webster's Revised Unabridged Dictionary (1913)

Adamantine \Ad`a*man"tine\, a. [L. adamantinus, Gr. ?.]
   1. Made of adamant, or having the qualities of adamant;
      incapable of being broken, dissolved, or penetrated; as,
      adamantine bonds or chains.

   2. (Min.) Like the diamond in hardness or luster.

Source : WordNet®

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}]