sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5–7 on Mohs scale; Color: Dark browns, blacks, and greys with visible linear graining; Luster: Waxy to dull (vitreous when polished); Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific gravity: 2.6–2.9.

Hardness: 6
Color: Dark browns, blacks, and greys with visible linear graining
Luster: Waxy to dull (vitreous when polished)

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure. This specimen likely dates back to the Cenozoic or Mesozoic eras, forming in anaerobic environments like volcanic ash beds or river sediments.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), interior decor, bookends, and as educational/geological collectibles.

Geological facts

Petrified wood is the state fossil of Arizona and several other US states. Every cell of the original plant can sometimes be preserved in silica, allowing researchers to identify ancient tree species under a microscope.

Field identification & locations

Identify in the field by looking for 'rock logs' or fragments that show wood-like textures, growth rings, or bark patterns but feel heavy and cold like stone. It frequently occurs in badlands or areas with ancient sedimentary deposits.

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