Bible Verses About Adamant: A flint.

Yes, I am making your resoluteness harder than flint, as hard as a diamond. So don't be afraid of them or depressed by how they look at you, because they are a rebellious house."

Yes, they made their hearts as hard as a diamond, so that they wouldn't hear the Torah and the messages that ADONAI-Tzva'ot had sent by his Spirit through the earlier prophets. This is why great anger came from ADONAI-Tzva'ot;