Petrified Wood is wood that chemically replaced
by a mineral substance. The replacement is usually Chalcedony
, but Opal
and a few other minerals are also known to replace the wood. When the wood becomes petrified, its original mold remains intact, but an entire new substance takes the place of what was once wood. When the mineral replacement of the wood is Chalcedony or Opal, the substance is also called "Silicafied Wood".