'Iron' in the Bible

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

They are all grievous revolters, 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 shall ye 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 graven upon the tablet of their heart, and upon the horns of your altars;

Go, and tell Hananiah, saying, Thus saith Jehovah: Thou hast broken the bars of wood; but thou hast made in their stead bars of iron.

For thus saith Jehovah of hosts, the God of Israel: I have put a yoke of iron upon the neck of all these nations, that they may served Nebuchadnezzar king of Babylon; and they shall serve him: and I have given him the beasts of the field also.