mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: brown, tan, grey with white quartz vein; Luster: waxy to vitreous; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.6–2.9

Hardness: 6
Color: brown, tan, grey with white quartz vein
Luster: waxy to vitreous

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: brown, tan, grey with white quartz vein; Luster: waxy to vitreous; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.6–2.9

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (primarily silica) over millions of years, often in volcanic ash beds or river sediments during the Mesozoic or Cenozoic eras.

Uses & applications

Used in high-end furniture (slabs), jewelry making (cabochons), lapidary art, and as a popular collector's specimen for display.

Geological facts

Petrified wood is the state gemstone of Washington and Arizona. While it looks like wood, it is actually a fossil stone where every cell has been replaced by quartz or chalcedony.

Field identification & locations

Identify by the presence of wood-like grain patterns, rings, or bark textures combined with a stony hardness that cannot be scratched by a steel knife. Common in the Western US.