ADAMANT
adamant, adamantine, inexorable, intransigent
(adjective) 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”
diamond, adamant
(noun) very hard native crystalline carbon valued as a gem
Source: WordNet® 3.1
Etymology
Adjective
adamant (comparative more adamant, superlative most adamant)
(said of people and their conviction) Firm; unshakeable; unyielding; determined.
(of an object) Very difficult to break, pierce, or cut.
Synonyms
• See also obstinate
Noun
adamant (plural adamants)
An imaginary rock or mineral of impenetrable hardness; a name given to the diamond and other substances of extreme hardness.
An embodiment of impregnable hardness.
(obsolete) A lodestone.
Source: Wiktionary
Ad"a*mant, n. Etym: [OE. adamaunt, adamant, diamond, magnet, OF.
adamant, L. adamas, adamantis, the hardest metal, fr. Gr. adamare to
love, be attached to, the word meant also magnet, as in OF. and LL.
See Diamond, Tame.]
1. A stone imagined by some to be of impenetrable hardness; a name
given to the diamond and other substance of extreme hardness; but in
modern minerology it has no technical signification. It is now a
rhetorical or poetical name for the embodiment of impenetrable
hardness.
Opposed the rocky orb Of tenfold adamant, his ample shield. Milton.
2. Lodestone; magnet. [Obs.] "A great adamant of acquaintance."
Bacon.
As true to thee as steel to adamant. Greene.
Source: Webster’s Unabridged Dictionary 1913 Edition