fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 7 on the Mohs scale, vitreous to waxy luster, amorphous crystal structure (quartz/chalcedony), conchoidal fracture with no true cleavage, specific gravity ranges from 2.5 to 2.65, displays distinctive wood grain textures and colors such as brown, red, yellow, and black.

Identified August 2, 2026More fossil →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in low-oxygen, mineral-rich sediment, usually volcanic ash or river floodplains. Over millions of years, groundwater rich in dissolved silica percolates through the wood, replacing the organic cellular structure with quartz, opal, or chalcedony while preserving the original microscopic details. Geological age ranges from the Carboniferous period to recent epochs, with famous deposits dating back over 200 million years to the Triassic.

Uses & applications

Used primarily for lapidary work, making decorative objects, bookends, tabletop surfaces, cabochons for jewelry, and valued as a collectible mineral and fossil specimen.

Geological facts

Petrified wood can retain its cellular structure so perfectly that scientists can identify the exact ancient tree species using a microscope. The Petrified Forest National Park in Arizona contains some of the most famous and extensive deposits in the world.

Field identification & locations

Can be identified in the field by its wood-like appearance combined with an unusually heavy weight, cold touch, and a glassy or quartz-like hardness that cannot be scratched with a steel knife. Commonly found in sedimentary layers, desert basins, and areas with historical volcanic activity.