sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, beige, brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline quartz/chalcedony); Cleavage: None; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Tan, beige, brown
Luster: Vitreous to dull

Identified May 31, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, beige, brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline quartz/chalcedony); Cleavage: None; Specific Gravity: 2.6-2.9

Formation & geological history

Formed via permineralization where organic wood is replaced by silica minerals, typically quartz or opal, over millions of years in anaerobic conditions often under volcanic ash or sedimentary layers.

Uses & applications

Commonly used for lapidary work, jewelry, interior design (tabletops/bookends), and as an educational or decorative geological specimen.

Geological facts

The organic structure is often so well preserved that tree rings and cellular details are visible. Famous locations include the Petrified Forest National Park in Arizona, USA.

Field identification & locations

Identify by looking for wood grain patterns, knot structures, or bark textures in a heavy, stony material. Commonly found in sedimentary basins and areas with historical volcanic activity.