Petrified Wood is the result of a process called petrifaction (or petrification), meaning "to change into stone." The process involves mineral emplacement, in which dissolved minerals are carried by groundwater into the porous parts of buried wood (or shells or bones), where they crystallize out and settle, filling the pores.  Also referred to as 'agatized wood'.  I personally like to use Petrified wood for the wonderful grounding effect it offers.  It is important to have on hand when one is feeling 'light headed' from Reiki or other healing modalities.  Keeps one grounded with the energy of the Earth.  Also to be used in Native American ceremonies. These are perfect slabs.....................from old stock!