Job 19:24
That they were graven with an iron pen and lead in the rock for ever!
Torrey's Topical Textbook—AKJV

Jeremiah 17:1
The sin of Judah is written with a pen of iron, and with the point of a diamond: it is graven on the table of their heart, and on the horns of your altars;
Torrey's Topical Textbook—AKJV