As true to thee as steel to adamant.
Greene.
Ad`a*man*te"an (&?;), a. [L. adamantus.] Of adamant; hard as adamant. Milton.
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.