mineral

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: Brown, tan, cream, and grey; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (microscopic quartz/chalcedony); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.9.

Hardness: 6
Color: Brown, tan, cream, and grey
Luster: Vitreous to waxy

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood is gradually replaced by silica (quartz) from groundwater while buried under sediment or volcanic ash. This specimen likely dates from the Triassic to the Neogene period (200 million to 2 million years ago).

Uses & applications

Used in jewelry (cabochons), interior design (polished bookends, tables), and popular as educational and aesthetic fossils for collectors.

Geological facts

In some specimens, the replacement is so precise that microscopic structures like tree rings and individual plant cells remain visible. The largest concentration of these specimens is in the Petrified Forest National Park in Arizona.

Field identification & locations

Identify in the field by looking for bark-like external textures combined with a heavy, rock-like weight and glassy internal fracture appearance. Common in areas with ancient sedimentary basins or volcanic deposits like Arizona, Oregon, and Madagascar.