sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony - SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Tan, brown, and grey with black mineral inclusions. Luster: Waxy to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Tan, brown, and grey with black mineral inclusions
- Luster
- Waxy 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 on Mohs scale. Color: Tan, brown, and grey with black mineral inclusions. Luster: Waxy to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization where organic wood is buried by sediment or volcanic ash. Over millions of years (often from the Triassic, Jurassic, or Cretaceous periods), groundwater rich in silica flows through the sediment, replacing the plant material with minerals while preserving the anatomical structure.
Uses & applications
Used in ornamental jewelry (cabochons), interior design (tabletops and bookends), lapidary art, and as a popular educational/collectible item for geological enthusiasts.
Geological facts
Petrified wood is the state fossil of Arizona, home to the Petrified Forest National Park. Because the wood is replaced by quartz, it can actually be millions of years old while appearing remarkably similar to fresh wood grain.
Field identification & locations
Identify in the field by looking for 'tree ring' patterns or bark-like textures in a rock that is too hard to be scratched by a steel knife. Common in volcanic areas and sedimentary basins. Collectors should look for preserved cell structures or 'knots' in the wood.
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