Select a special material, such as adamantine. Your attacks take on the quality of that material even without a weapon made of it.
Benefit: The character’s melee weapons (including natural weapons) are treated as being crafted from the chosen special material for the purposes of bypassing the damage reduction of any creature the character strikes. None of the other special properties of special materials are gained by the character’s melee weapons.
Special: A character can gain this feat multiple times. Each time the feat is selected the character selects a different special material. The character’s melee attacks are treated as being crafted of all chosen materials for the purposes of bypassing damage reduction.
Source: Standard Reference Document under Open Game License v1.0a, which updated this feat originally published in the Epic Level Handbook, page 63.