(Jer. 17:13; Ezek. 4:1) Clay tablets were made of clean washed, smooth clay. While still wet, the clay had wedge shaped letters (now called "cuneiform" from the Latin cuneus, meaning "wedge") imprinted on it with a stylus, and then was kiln fired or sun dried. Tablets were made of various shapes --- cone-shaped, drum-shaped, and flat. They were often placed in clay envelopes
The oldest ones go back to 3,000 B.C. They are practically imperishable; fire only hardens them the more. Many of the clay tablets found do much to verify the truthfulness of the Biblical record.