sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, cream, and grey with distinct wood-grain patterns, Luster: Vitreous to waxy, Crystal structure: Trigonal/Amorphous (Cryptocrystalline quartz/Chalcedony replacement), Cleavage: None, Specific gravity: 2.6-2.9

Hardness: 6

Identified June 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic wood materials are replaced by minerals (usually silica) over millions of years while buried under sediment or volcanic ash. It dated from the Devonian period to the Holocene.

Uses & applications

Used frequently for decorative items, jewelry (cabochons), furniture tops, and as geological museum or collector specimens.

Geological facts

The Petrified Forest National Park in Arizona is one of the most famous locations for this specimen. It is not actually wood, but a fossilized mineral replica of what was once a living tree.

Field identification & locations

Identify by looking for preserved growth rings, bark textures, or cell structures. Commonly found in areas with ancient volcanic activity and sedimentary basins. Look for rectangular or log-like fractures and heavy, dense feel compared to regular wood.