fossil

Petrified Wood

Silicified Wood (primarily SiO2)

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

Hardness: 6
Color: Brown, tan, cream, and grey
Luster: Vitreous to waxy

Identified July 2, 2026More fossil →

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Physical properties

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

Formation & geological history

Formed via permineralization where organic wood material is replaced by minerals, typically silica (quartz or chalcedony), over millions of years after being buried in sediment or volcanic ash. Common in strata from the Triassic to the Tertiary periods.

Uses & applications

Used for decorative items, jewelry (cabochons), furniture (table tops), and as a popular collector specimen for educational and aesthetic value.

Geological facts

The colors in petrified wood are caused by trace elements: iron produces reds and yellows, manganese produces pinks or blacks, and copper or chrome produce greens and blues.

Field identification & locations

Identify by looking for preserved wood grain, bark patterns, or growth rings in a heavy, stone-like material. Found globally in locations like the Petrified Forest National Park (USA), Madagascar, and Indonesia.