fossil

Petrified Wood

Silicified Wood (Permineralized wood)

Hardness: 6.5-7 (Mohs scale), Color: tan, brown, and grey, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (usually replaced by quartz/chalcedony), Cleavage: None

Hardness: 6

Identified July 17, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, brown, and grey, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (usually replaced by quartz/chalcedony), Cleavage: None

Formation & geological history

Formed when plant material is buried by sediment and protected from decay by oxygen and organisms. Groundwater rich in dissolved solids (like silica) flows through the sediment, replacing the original plant material with inorganic material. Usually Mesozoic to Cenozoic eras.

Uses & applications

Collecting, jewelry (lapidary), decorative bookends, furniture tops, and educational displays.

Geological facts

In petrified wood, the organic material is often replaced by minerals so perfectly that the tree's internal structure, including bark and growth rings, is preserved in stone.

Field identification & locations

Identify by looking for bark-like textures or growth rings on a stone that is much heavier/harder than wood. Common in the western USA (notably Arizona), Madagascar, and Indonesia.