mineral

Petrified Wood

Silicified Wood (SiO2 - Silicon Dioxide)

Hardness: 6.5–7 on the Mohs scale. Color: Brown, tan, red, yellow, and black. Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline (Microcrystalline Quartz). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.

Hardness: 6
Color: Brown, tan, red, yellow, and black
Luster: Vitreous to waxy

Identified March 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed through permineralization, where organic wood is gradually replaced by silica-rich water over millions of years (often Triassic or Jurassic periods, 200+ million years ago). The wood is typically buried under volcanic ash or sediment, creating an anaerobic environment that prevents decay.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), ornamental furniture (table slabs), and as display specimens for collectors.

Geological facts

Petrified wood is the state fossil of Arizona, home to the famous Petrified Forest National Park. The colors are created by trace elements: iron produces reds and yellows, manganese produces pinks or oranges, and carbon produces black.

Field identification & locations

Identify by looking for preserved wood grain, bark textures, and annual growth rings in a heavy, stony material. Common in dry regions like Arizona, Utah, and Madagascar. Collectors should look for 'knots' or distinct cell structures under magnification.

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