Petrified wood is actually a fossil. It forms when plant material becomes buried by sediment. Oxygen and organisms protect it from decay and eventually groundwater that is rich in dissolved solids flows through the sediment and replaces the original plant material with minerals such as calcite, quartz, agate, pyrite and sometimes opal.
Metaphysically, petrified wood is a powerful stone for protection, grounding and healing. It is known as the fruition stone, especially where business and achieving goals are concerned, it is also believed to enhance patience while waiting to reach those goals. It is said it calms the nerves, improves energy flow and encourages inner transformation.