sedimentary

Petrified Wood

Silicified Wood (SiO2 - Quartz/Chalcendony replacing organic matter)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale. Color: Highly variable, featuring reds, browns, oranges, and blacks (due to iron and manganese). Luster: Vitreous to waxy. Crystal Structure: Cryptocrystalline (Microcrystalline quartz). Cleavage: None; exhibits conchoidal fracture.

Hardness: 6
Luster: Vitreous to waxy

Identified February 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization over millions of years (often Triassic or Jurassic periods). Organic matter is buried under sediment where volcanic ash provides silica. Groundwater dissolves the organic material, replacing it with minerals like quartz or chalcedony. Total process takes 5 to 100 million years.

Uses & applications

Commonly used for decorative lapidary work, high-end furniture (slabs), jewelry (cabochons), and as museum or collector display specimens.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona. In some cases, the replacement is so precise that the internal cellular structure of the original tree and wood grain is visible under a microscope.

Field identification & locations

Identify in the field by looking for a 'bark-like' exterior texture with a dense, heavy, stony interior that breaks like glass. Commonly found in arid landscapes where ancient riverbeds or volcanic ash layers are exposed, such as the American Southwest, Argentina, and Madagascar.