sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5 to 7 on Mohs scale; Color: Multi-colored bands (browns, reds, yellows); Luster: Sub-vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline quartz); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Multi-colored bands (browns, reds, yellows)
Luster: Sub-vitreous to waxy

Identified July 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization or replacement where organic wood tissue is replaced with silicate minerals (usually chalcedony or opal) in the absence of oxygen. Typically found in volcanic ash-rich sedimentary layers from the Paleozoic to the Cenozoic eras.

Uses & applications

Used for decorative items, jewelry (cabochons), furniture tops, and as a popular specimen for mineral collectors.

Geological facts

The colors in petrified wood are caused by trace elements: iron oxides produce reds and yellows, while manganese generates pinks or blacks. The Petrified Forest National Park in Arizona is one of the most famous locations for these fossils.

Field identification & locations

Identify in the field by looking for wood-like grain patterns, bark textures, or annual growth rings preserved in stone. It is often found in badlands or areas with high erosion of sedimentary layers.