sedimentary

Petrified Wood

Silicified wood (primarily Silicon Dioxide, SiO2)

Hardness: 6.5–7 on Mohs scale; Color: Tan, brown, and cream tones with reddish-orange iron staining; Luster: Waxy to dull (vitreous when polished); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9

Hardness: 6
Luster: Waxy to dull (vitreous when polished)

Identified March 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood is replaced by silica-rich minerals (like jasper, chalcedony, or opal) in low-oxygen environments. These specimens often originate from the Triassic period (approx. 225 million years ago) or the Cenozoic era.

Uses & applications

Used primarily for ornamental displays, jewelry (cabochons), interior design (furniture tops), and as significant geological/paleontological educational specimens.

Geological facts

Petrified wood is the state gemstone of Washington and the state fossil of Arizona. While the organic matter is gone, the internal structure including tree rings and cell walls are often perfectly preserved in stone.

Field identification & locations

Identify by looking for bark-like textures on the exterior and visible growth rings or wood grain patterns on the cross-section. Common in the western USA (Arizona's Painted Desert), Madagascar, and Indonesia. Collectors should look for high-contrast colors and intact structural details.

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