fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Black, grey, white, tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Quartz/Chalcedony); Cleavage: Conchoidal fracture; Growth rings visible.

Hardness: 6
Color: Black, grey, white, tan
Luster: Waxy to vitreous

Identified July 15, 2026More fossil →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Black, grey, white, tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Quartz/Chalcedony); Cleavage: Conchoidal fracture; Growth rings visible.

Formation & geological history

Formed through permineralization where organic matter is replaced by silica (usually from volcanic ash) in an anaerobic environment, typically dating from the Devonian to the Holocene (millions of years ago).

Uses & applications

Used for ornamental display, lapidary work (jewelry, bookends, tabletops), and as scientific specimens for studying paleobotany.

Geological facts

The colors are caused by trace elements: iron produces reds/yellows, while carbon or manganese can produce dark blacks and greys. The Arizona Petrified Forest is one of the most famous sites worldwide.

Field identification & locations

Identify by looking for preserved plant structures like bark textures or annual growth rings. Commonly found in sedimentary basins and areas with historical volcanic activity. Collectors look for high contrast and intact cell structure.