Rock Identifier
Petrified Wood (Silicified Wood (SiO2)) — fossil
fossil

Petrified Wood

Silicified Wood (SiO2)

AI-generated identification · may be incorrect

Mohs hardness: 6.5-7. Color: Tan, beige, brown, light yellow. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (microcrystalline quartz/chalcedony replacing organic structure). Cleavage: None (conchoidal fracture). Specific gravity: ~2.6.

Hardness
6
Color
Tan, beige, brown, light yellow
Luster
Waxy to dull
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Physical properties

Mohs hardness: 6.5-7. Color: Tan, beige, brown, light yellow. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (microcrystalline quartz/chalcedony replacing organic structure). Cleavage: None (conchoidal fracture). Specific gravity: ~2.6.

Formation & geological history

Formed via permineralization, where organic wood material buried rapidly under sediment or volcanic ash is gradually replaced by silica-rich groundwater. Over millions of years, the cellular structure of the wood is preserved in quartz.

Uses & applications

Popular for lapidary work, jewelry making, decorative bookends, stone carvings, and educational fossil collections.

Geological facts

Petrified wood can retain detailed tree rings, bark textures, and cellular structures under microscopic view. Arizona's Petrified Forest National Park is one of the world's most famous localities for it.

Field identification & locations

Identified in the field by looking like a piece of dry wood or tree bark, but feeling significantly heavier and hard like stone, refusing to scratch with steel. Found in sedimentary rock formations and alluvial deposits globally.

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