'Brass' in the Bible

I will go before thee, and make the rough places smooth; I will break in pieces the doors of brass, and cut in sunder the bars of iron;

Because I knew that thou art obstinate, and thy neck is an iron sinew, and thy brow brass;

For brass I will bring gold, and for iron I will bring silver, and for wood brass, and for stones iron. I will also make thy officers peace, and thine exactors righteousness.