sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
Hardness: 6.5–7 (Mohs scale); Color: tan, brown, beige with some gray; Luster: vitreous to dull; Crystal structure: cryptocrystalline (chalcedony/quartz); no cleavage; specific gravity approx. 2.6.
- Hardness
- 6
- Color
- tan, brown, beige with some gray
- Luster
- vitreous to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5–7 (Mohs scale); Color: tan, brown, beige with some gray; Luster: vitreous to dull; Crystal structure: cryptocrystalline (chalcedony/quartz); no cleavage; specific gravity approx. 2.6.
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (usually silica) from groundwater while buried under sediment or volcanic ash. This process typically takes millions of years, often dating back to the Triassic or Jurassic periods.
Uses & applications
Used for ornamental jewelry (cabochons), interior decoration (furniture, bookends), and highly sought after by geological collectors for its preservation of biological structures.
Geological facts
Petrified wood is the state gem of Washington and the state fossil of Arizona. The cell structure of the original tree is often so perfectly preserved that the species of tree can be identified by paleontologists.
Field identification & locations
Identify in the field by looking for 'fossilized' bark patterns and wood grain textures on the surface of heavy, rock-like fragments. Commonly found in arid regions like Arizona, Utah, and parts of the Pacific Northwest.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary