'Iron' in the Bible

Now behold, I have made you today like a fortified city and like an iron pillar and like bronze walls against the whole land—against the [successive] kings of Judah, against its leaders, against its priests, and against the people of the land [giving you divine strength which no hostile power can overcome].

They are all the worst [kind] of [stiff-necked, godless] rebels,Going around spreading slander.They are [not gold and silver ore, but] bronze and iron;They are all corrupt.

which I commanded your fathers at the time that I brought them out of the land of Egypt, from the iron furnace, saying, ‘Listen to My voice and do according to all that I command you. So you shall be My people, and I will be your God,’

“Can anyone crush iron,The iron from the north, or bronze?

The sin of Judah is written down with an iron stylus;With a diamond point it is engraved upon the tablet of their heartAnd on the horns of their altars.

“Go and tell Hananiah, ‘The Lord says this, “You have broken yokes of wood, but you have made in their place bars of iron.”

For thus says the Lord of hosts, the God of Israel, “I have put the iron yoke [of servitude] on the neck of all these nations, that they may serve Nebuchadnezzar king of Babylon; and they will serve him. And I have even given him the beasts of the field.”’”