SRD:Ironwood

Ironwood is a magical substance created by druids from normal wood. While remaining natural wood in almost every way, ironwood is as strong, heavy, and resistant to fire as steel. Spells that affect metal or iron do not function on ironwood. Spells that affect wood do affect ironwood, although ironwood does not burn. Using this spell with wood shape or a wood-related Craft check, you can fashion wooden items that function as steel items. Thus, wooden plate armor and wooden swords can be created that are as durable as their normal steel counterparts. These items are freely usable by druids.

Further, if you make only half as much ironwood as the spell would normally allow, any weapon, shield, or suit of armor so created is treated as a magic item with a +1 enhancement bonus.

Material Component: Wood shaped into the form of the intended ironwood object.