'Iron' in the Bible

For, behold, I have made you this day a fortified city, and an iron pillar, and bronze walls, against the whole land, against the kings of Judah, against its princes, against its priests, and against the people of the land.

They are all grievous rebels, going about with slanders; they are brass and iron: they all of them deal corruptly.

which I commanded your fathers in the day that I brought them forth out of the land of Egypt, out of the iron furnace, saying, Obey my voice, and do them, according to all which I command you: so you shall be my people, and I will be your God;

Can one break iron, even iron from the north, and brass?

The sin of Judah is written with a pen of iron, [and] with the point of a diamond: it is engraved on the tablet of their heart, and on the horns of your altars;

Go, and tell Hananiah, saying, Thus says Yahweh: You have broken the bars of wood; but you have made in their place bars of iron.

For thus says Yahweh of Armies, the God of Israel: I have put a yoke of iron on the neck of all these nations, that they may serve Nebuchadnezzar king of Babylon; and they shall serve him: and I have given him the animals of the field also.