'Iron' in the Bible

And I, lo, I have given thee this day for a fenced city, and for an iron pillar, and for brazen walls over all the land, to the kings of Judah, to its heads, to its priests, and to the people of the land;

All of them are turned aside by apostates, Walking slanderously -- brass and iron, All of them are corrupters.

That I commanded your fathers, In the day of My bringing them out from the land of Egypt, Out of the iron furnace, saying, Hearken to My voice, and ye have done them, According to all that I command you, And ye have been to Me for a people, And I am to you for God,

Doth one break iron -- northern iron, and brass?

The sin of Judah is written with a pen of iron, With the point of a diamond, Graven on the tablet of their heart, And on the horns of your altars,

'Go, and thou hast spoken unto Hananiah, saying, Thus said Jehovah, Yokes of wood thou hast broken, and I have made instead of them yokes of iron;

For thus said Jehovah of Hosts, God of Israel, A yoke of iron I have put on the neck of all these nations to serve Nebuchadnezzar king of Babylon, and they have served him, and also the beast of the field I have given to him.'