Stonewood

This spell bestows the strength of stone on a given volume of wood without otherwise altering its appearance or weight. A wooden door or wall, for example, would have the sturdiness (and saving throws) of stone. The stonewood spell affects a maximum of 100 square feet of wood per level of the caster, to a thickness of 1 foot (or any equivalent numerical combination). Only one wooden object can be strengthened per casting.

The material components are a gemstone of at least S00 gp value and a small piece of hardwood.