Petrified Wood

Arizona State Fossil


Petrified wood log at Petrified Forest National Park AZ

Petrified wood log at Petrified Forest National Park; photo courtesy Free Public Domain Photo Database: Petrified Wood.

Petrified Wood

Arizona designated petrified wood (Araucarioxylon arizonicum) as the official state fossil in 1988.

Petrified Forest National Park in northern Arizona has one of the largest and most colorful concentrations of petrified wood in the world. Made up of almost solid quartz, each piece of petrified wood is like a giant crystal, often sparkling in the sunlight with a rainbow of colors.

How is Petrified Wood Formed?

Over 200 million years ago, the original logs were washed into an ancient river system and buried quickly by sediment so that oxygen was cut off and decay was slowed to a process that would take centuries. Minerals such as silica were absorbed into the porous wood over hundreds and thousands of years and crystallized within the cellular structure, replacing the organic material (petrified wood weighs as much as 150-200 pounds per cubic foot).



Petrified wood log; photo from free public domain

Petrified wood log


Rock hounds digging rainbow petrified wood Arizona