fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, grey, and cream. Luster: Vitreous to dull. Structure: Cryptocrystalline (chalcedony/quartz) preserving original cellular plant structure. Specific Gravity: 2.6-2.9.

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

Identified July 15, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood is replaced by silica (chalcedony) over millions of years. This usually occurs when trees are buried under volcanic ash or sediment in an anaerobic environment.

Uses & applications

Used for decorative ornaments, jewelry (cabochons), furniture (tabletops), and as highly collectible geological specimens.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. In some specimens, the replacement is so perfect that even individual tree rings and cell structures are visible under a microscope.

Field identification & locations

Identify by looking for wood-like textures such as bark patterns, knots, or growth rings in a heavy, stony material. Common in badlands and areas with ancient volcanic activity like Arizona, Oregon, and Madagascar.