fossil

Petrified Wood

Silicified Wood (Quartzo-feldspathic fossil wood)

Hardness: 7 on the Mohs scale; Color: Tan, brown, white, and dark grey variations; Luster: Vitreous to waxy when polished; Crystal structure: Trigonal (microcrystalline quartz/chalcedony); Cleavage: None (conchoidal fracture); Specific gravity: 2.5 - 2.7

Hardness: 7 on the Mohs scale
Color: Tan, brown, white, and dark grey variations
Luster: Vitreous to waxy when polished

Identified July 30, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization when buried organic material (wood) in an anoxic environment is slowly replaced by groundwater rich in dissolved silica (quartz, chalcedony, or opal) over millions of years, often dating from the Triassic period or younger.

Uses & applications

Used primarily in lapidary arts, making decorative items, bookends, jewelry, and prized by fossil and rock collectors worldwide.

Geological facts

Famous localities include the Petrified Forest National Park in Arizona, USA, where entire ancient forests were buried by volcanic ash and mineralized.

Field identification & locations

Identified easily by retaining the original cellular wood structure, growth rings, and bark texture despite being completely turned to solid stone. Found worldwide in sedimentary rock layers associated with ancient river floodplains or volcanic ash beds.

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