sedimentary

Petrified Wood

Silicon Dioxide (SiO2) permineralized organic matter

Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, black, and grey with wood-like grain patterns; Luster: Vitreous to waxy; Structure: Cryptocrystalline (replacing original cellular structure); Specific Gravity: 2.6–2.9

Hardness: 6
Color: Brown, tan, black, and grey with wood-like grain patterns
Luster: Vitreous to waxy

Identified April 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, where organic remains are replaced by minerals (usually silica) while retaining the original structure. This specimen likely dates from the Triassic to the Tertiary periods in an anaerobic environment like river sediments or volcanic ash beds.

Uses & applications

Used primarily for jewelry (cabochons), lapidary art, home decor (tabletops, bookends), and as educational or geological collectibles.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. In some cases, the replacement is so perfect that even individual cells and tree rings can be studied under a microscope.

Field identification & locations

Identify in the field by looking for characteristic 'bark' textures on the exterior and growth ring patterns on the interior. Often found in badlands, desert regions, or areas with prehistoric floodplains.

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