Adamant
Adamant (ad"ȧ*mant) , noun
[Old English adamaunt, adamant, diamond, magnet, Old French adamant, Latin adamas, adamantis, the hardest metal, from Greek 'ada`mas, -antos; 'a priv. + dama^,n to tame, subdue. In Old English, from confusion with Latin adamare to love, be attached to, the word meant also magnet, as in Old French and Late Latin See Diamond, Tame.]
1.
A stone imagined by some to be of impenetrable hardness; a name given to the diamond and other substances of extreme hardness; but in modern mineralogy 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.
2.
Lodestone; magnet. [Obsolete]
A great adamant of acquaintance.
As true to thee as steel to adamant.