Fossilized - or petrified - wood is a mineral, where all of the original plant material has been replaced by silica, pyrite, calcite or another inorganic material. It occurs when plant material is buried under sediment, protected from oxygen and other elements, then experiences mineral-rich groundwater flowing through the sediment, gradually producing a fossil of the orginal material that bears fossilized details of the bark, wood and cellular structures. It is incredibly beautiful and fascinating to look at and I have in stock some strands of beads in differerent sizes, all with the same soft, silky matt finish. It is amazing stuff, as it really does look exactly like wood but has the coolness and weight of stone. Has to be seen to be believed!