sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, grey, green, and red; Luster: Dull to waxy; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9

Hardness: 6
Color: Variegated brown, grey, green, and red
Luster: Dull to waxy

Identified June 9, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, grey, green, and red; Luster: Dull to waxy; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9

Formation & geological history

Formed via permineralization where organic plant material is replaced by minerals, typically silica (chalcedony or opal), over millions of years after burial in volcanic ash or sediments. Most often from the Triassic to Eocene periods.

Uses & applications

Commonly used in jewelry (cabochons), interior design (tables, bookends), ornamental carvings, and as a popular geological collectible.

Geological facts

The colors in petrified wood are caused by trace elements; for example, iron produces reds and yellows, manganese produces pinks or oranges, and copper or cobalt produces greens and blues.

Field identification & locations

Identify in the field by looking for stone specimens that retain wood grain patterns, bark textures, or annual growth rings. Commonly found in Arizona (USA), Madagascar, and Brazil. Always check local laws as collecting fossils is often restricted.