mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish, Luster: Vitreous to waxy, Crystal Structure: Amorphous or Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9

Hardness: 6

Identified June 19, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish, Luster: Vitreous to waxy, Crystal Structure: Amorphous or Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic matter is replaced by minerals (usually silica) while retaining original wood structure. Common in the Triassic and Jurassic periods in river basins and volcanic ash deposits.

Uses & applications

Used for ornamental furniture, jewelry (cabochons), paperweights, and highly valued as geological display specimens.

Geological facts

The wood is not actually wood anymore but a stone fossil. Some specimens retain cellular details so clear they can be used to identify the specific prehistoric tree species.

Field identification & locations

Look for visible wood grain, growth rings, or bark textures on the exterior. Found globally, with famous deposits in Arizona (USA), Madagascar, and Argentina.