sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs). Color: Brown, tan, and grey with wood-grain texture. Luster: Dull to waxy. Structure: Cryptocrystalline quartz (Chalcedony/Opal). Cleavage: None. Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, and grey with wood-grain texture
Luster: Dull to waxy

Identified May 20, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs). Color: Brown, tan, and grey with wood-grain texture. Luster: Dull to waxy. Structure: Cryptocrystalline quartz (Chalcedony/Opal). Cleavage: None. Specific Gravity: 2.6-2.9.

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic conditions under sediment layers, often millions of years ago (Mesozoic to Cenozoic eras).

Uses & applications

Used for decorative items, bookends, jewelry (cabochons), landscape architecture, and as educational scientific specimens.

Geological facts

Depending on the minerals present, petrified wood can turn vibrant colors: iron produces reds and yellows, while manganese produces pinks or blacks. The largest concentration is found in the Petrified Forest National Park, Arizona.

Field identification & locations

Identify in the field by looking for distinct tree ring structures, bark textures, and woody fiber patterns preserved in stone. Found globally in ancient riverbeds and volcanic ash deposits.