mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, red, grey, or tan depending on mineral impurities. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, red, grey, or tan depending on mineral impurities
Luster: Vitreous to waxy

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Brown, red, grey, or tan depending on mineral impurities. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Formation & geological history

Formed through permineralization, a process where organic wood cells are replaced by silica-rich water over millions of years, often in volcanic ash beds or sedimentary basins dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used for jewelry (cabochons), interior decoration (slabs, bookends, furniture), and as highly prized geological specimens for collectors.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. The organic matter can be replaced so perfectly that microscopic tree ring structures remain visible.

Field identification & locations

Identify by looking for wood grain, bark textures, or growth rings in a heavy, stony material. Commonly found in Arizona (USA), Madagascar, and Indonesia. Collectors look for vibrant colors and intact cell structure.