'Diamond' in the Bible

the second row a turquoise, a sapphire, and a diamond;

and the second row, a turquoise, a sapphire, and a diamond;

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.

I have made your forehead like emery (diamond), harder than flint. Do not be afraid of them or be dismayed before them, though they are a rebellious house.”

They made their hearts [hard] like flint, so that they could not hear the law and the words which the Lord of hosts had sent by His Spirit through the former prophets. Therefore great wrath came from the Lord of hosts.