sedimentary

Petrified Wood

Silicified Wood (primarily Chalcedony or Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish-orange
Luster: Waxy to vitreous

Identified June 27, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None; Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure of the wood. This typically occurs in sedimentary environments under volcanic ash or water saturation, often dating back to the Mesozoic or Cenozoic eras.

Uses & applications

Used primarily for decorative furniture, lapidary items (cabochons), jewelry, and as educational geological or fossil specimens.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona, which contains wood from the Triassic period (approx. 225 million years ago). Different colors are caused by trace elements: iron yields red/brown, manganese yields pink/orange, and copper/cobalt can yield greens or blues.

Field identification & locations

Identify in the field by looking for distinct bark-like textures, growth rings, and wood grain paired with high density and extreme hardness. Common in badlands or areas with high volcanic ash deposits.