adamantine

From Middle English adamantine, adamantyne, adamauntyn (“(adjective) of adamant; (noun) adamant”), from Anglo-Norman adamantin and Middle French adamantin (“of or resembling adamant or diamond”) (modern French adamantin), and from its etymon Latin adamantinus (“adamantine”), from Ancient Greek ἀδᾰμάντῐνος (adămántĭnos, “hard as adamant; made of steel”), from ᾰ̓δᾰμᾰντ- (ădămănt-) (a stem of ἀδάμᾱς (adámās, “the hardest metal (probably steel); diamond”), possibly originally Semitic) + -ῐνος (-ĭnos, suffix meaning ‘made of’ forming adjectives). By surface analysis, adamant + -ine (suffix meaning ‘of or pertaining to’ forming adjectives). Etymology 1 sense 1.2.4 (“having the quality of attracting or drawing”) and etymology 1 sense 2 (“like diamond in lustre; etc.”) refer to adamant (“(archaic) lodestone; (historical, poetic) diamond”).

Possibly from adamantium + -ine (suffix forming the names of chemical substances or materials).