sedimentary

Petrified Wood

Silicified wood (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, grey, and black with visible grain patterns; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (chalcedony/quartz replacement); Cleavage: None; Specific gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, grey, and black with visible grain patterns
Luster: Vitreous to waxy

Identified June 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) from groundwater while buried in sediment/volcanic ash. Often dates from the Paleozoic to the Cenozoic eras.

Uses & applications

Used primarily for jewelry (cabochons), interior decoration (tabletops, bookends), and as collector specimens in lapidary arts.

Geological facts

In petrified wood, the replacement process is often so precise that cellular structures and growth rings of the original tree are perfectly preserved in stone.

Field identification & locations

Identify by looking for wood-like grain, bark textures, or growth rings on an object that is clearly stone. Commonly found in areas with ancient volcanic activity and sedimentary basins like Arizona's Petrified Forest.