This specimen formed about 200 million years ago, in an area near today's Arizona Petrified Forest. The area was was a lush, subtropical forest with massive conifer-like trees (like Araucarioxylon arizonicum), ferns, and other vegetation.
These trees fell—either due to age, storms, or floods—and were quickly buried by volcanic ash, mud, and sediment from nearby highlands and river systems. This rapid burial protected them from decay and oxygen exposure.
Over time, groundwater rich in dissolved silica (from volcanic ash) seeped through the sediment. As it percolated through the wood the wood’s organic material gradually decayed and Silica (SiO₂) replaced the organic structure cell-by-cell, preserving microscopic details of the wood grain.