Rock Identifier
Petrified Wood (Silicified Wood (mainly Quartz/Chalcedony, SiO2)) — fossil
fossil

Petrified Wood

Silicified Wood (mainly Quartz/Chalcedony, SiO2)

Hardness: 6.5-7 on the Mohs scale. Color: Brown, tan, reddish-brown, grey. Luster: Waxy to dull, glass-like when polished. Cleavage: None (conchoidal fracture). Retains original tree bark and wood grain textures.

Hardness
6
Color
Brown, tan, reddish-brown, grey
Luster
Waxy to dull, glass-like when polished
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Physical properties

Hardness: 6.5-7 on the Mohs scale. Color: Brown, tan, reddish-brown, grey. Luster: Waxy to dull, glass-like when polished. Cleavage: None (conchoidal fracture). Retains original tree bark and wood grain textures.

Formation & geological history

Formed through permineralization, where organic materials of buried trees are replaced by silica-rich water deposits over millions of years (typically Triassic to Neogene periods).

Uses & applications

Used for ornamental carvings, decorative lapidary displays, bookends, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood is the state stone of Washington and Mississippi, and the state fossil of North Dakota. The Petrified Forest National Park in Arizona is famous for colorful specimens rich in iron and manganese oxides.

Field identification & locations

Identified by its distinct wood grain and bark-like outer texture combined with the weight, coldness, and hardness of quartz stone. Commonly found in ancient river basins, volcanic ash beds, and sedimentary rock deposits globally.

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