From D&D Wiki
|This material is published under the OGL|
This rare magic wood is as hard as normal wood but very light. Any wooden or mostly wooden item (such as a bow, an arrow, or a spear) made from darkwood is considered a masterwork item and weighs only half as much as a normal wooden item of that type. Items not normally made of wood or only partially of wood (such as a battleaxe or a mace) either cannot be made from darkwood or do not gain any special benefit from being made of darkwood. The armor check penalty of a darkwood shield is lessened by 2 compared to an ordinary shield of its type. To determine the price of a darkwood item, use the original weight but add 10 gp per pound to the price of a masterwork version of that item.
Darkwood has 10 hit points per inch of thickness and hardness 5.
COST=Masterwork Item Cost + (10 × original lb. weight) gp