Darkwood

This rare magic wood is harder then 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 or suit of armor is lessened by 2 compared to an ordinary item 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.

Benefits:
 * +1 higher hardness ratings when compared to equivalent ones made of wood.
 * Armor check penalty lessened by 2
 * Weight cut in half
 * Since it is not metal it is immune to the attacks of creatures that may damage metal, like Rust Monsters.

Also, certain classes that have prohibitions against wearing metal armor, like Druids, can wear Darkwood armor freely.