mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 7 (Mohs scale); Color: Gray, tan, white, brown; Luster: Waxy or vitreous; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific Gravity: 2.6–2.9; Fracture: Conchoidal; Cleavage: None.

Hardness: 7 (Mohs scale)
Color: Gray, tan, white, brown
Luster: Waxy or vitreous

Identified May 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals, typically silica (chalcedony or quartz), in an anaerobic environment like volcanic ash or waterlogged sediments. These specimens often date back to the Triassic or Neogene periods.

Uses & applications

Used for jewelry (cabochons), lapidary art, decorative bookends, furniture tops, and as geological display specimens.

Geological facts

Petrified wood is the state fossil of Washington and Arizona. Famous locations like the Petrified Forest National Park in Arizona contain entire fossilized landscapes where organic cellular detail has been perfectly preserved in stone.

Field identification & locations

Identify by looking for preserved wood grain, bark textures, or annual rings in a stone that is too hard to scratch with steel. Often found in riverbeds, badlands, and areas with high volcanic ash deposits. Collectors look for high color contrast and well-preserved cell structures.