fossil

Polished petrified wood

Silicified wood, chiefly microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness about 6.5–7; brown, tan, and dark gray colors with glossy vitreous luster. Quartz replaces the wood’s cellular structure, often preserving grain, growth rings, and branching patterns; cleavage is absent and specific gravity is about 2.6.

Identified September 7, 2026More fossil →

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Physical properties

Formation & geological history

Silica-rich groundwater gradually replaces buried wood, commonly during the Cenozoic (roughly 66 million years ago to present), though older examples occur. It forms in volcanic ash beds, floodplains, and sedimentary deposits.

Uses & applications

Used as a polished cabochon, ornamental stone, bookend, and collector specimen; large pieces are used decoratively rather than structurally.

Geological facts

The visible wood-like pattern reflects fossilized cellular anatomy, not painted veining. Common varieties include agatized, opalized, and jasperized wood.

Field identification & locations

Identify it by preserved wood grain combined with quartz-like hardness and a cool, glassy polish; it will scratch glass but not usually quartz. Important localities include Arizona, Madagascar, Indonesia, and Oregon.