fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5 - 7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz preserving original organic cellular structure; Specific Gravity: 2.6 - 2.8.

Hardness: 6
Color: Brown, tan, reddish-orange
Luster: Vitreous to waxy

Identified July 6, 2026More fossil →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood materials are replaced by silica (quartz) from groundwater over millions of years, usually in volcanic ash or sedimentary environments dating back to the Triassic or Carboniferous periods.

Uses & applications

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

Geological facts

The process occurs under anaerobic conditions to prevent rot. The specific colors are caused by trace elements: iron produces reds and oranges, while manganese produces pinks or blacks. Petrified Forest National Park in Arizona is one of the most famous sites.

Field identification & locations

Identify in the field by looking for distinct wood grain, bark textures, or growth rings in a heavy, stony material that cannot be scratched by a steel knife. Commonly found in areas with ancient volcanic activity and sedimentary basins.