From ancient Greek meaning "wood turned into rock", Petrified Wood is a form of fossilization where all the organic matter has been replaced by minerals (usually a silicate, such as quartz) during a process called permineralization. In order for wood to become petrified it must be completely covered by sediment, thereby depriving the wood of oxygen. Simultaneously, there must be a mineral rich water source close by. Over time, the water delivers the minerals into the cellular structure of the wood, replacing and combining the organic material, cell by cell, until the wood is transformed into stone. The color of each piece is dependent upon other minerals present in the locality at the time of fossilization. Streaks of warm browns and reds are indicative of iron oxides present during a specimen's fossilization process.