From DDO wiki
Monks receive the class feat Ki Strike: Adamantine at level 16, allowing them to bypass Adamantine damage reduction with unarmed attacks. Some loot-generated handwraps and named handwraps show "Adamantine lined" as a metal property.
- Light: 1/- damage reduction
- Medium: 2/- damage reduction
- Heavy: 3/- damage reduction
- Like weapons, armor made of Adamantine has a Hardness rating 10 points higher than equivalent steel armor.