fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs). Color: Brown, black, reddish-brown. Luster: Vitreous to waxy (when polished). Crystal system: Hexagonal/Amorphous. Specific gravity: 2.6-2.9. Exhibits wood grain textures.

Hardness: 6
Color: Brown, black, reddish-brown
Luster: Vitreous to waxy (when polished)

Identified July 10, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs). Color: Brown, black, reddish-brown. Luster: Vitreous to waxy (when polished). Crystal system: Hexagonal/Amorphous. Specific gravity: 2.6-2.9. Exhibits wood grain textures.

Formation & geological history

Formed through the process of permineralization where organic wood material is replaced by minerals, typically silica, over millions of years in anaerobic conditions like volcanic ash or waterlogged sediments.

Uses & applications

Used for decorative items, jewelry (cabochons), table tops, and as educational/collector specimens.

Geological facts

Unlike a typical fossil which is an impression, petrified wood is a three-dimensional replacement of the original plant tissue. It can preserve cellular structures so well that the tree species can often be identified.

Field identification & locations

Identify by wood-like grain, bark-like exterior textures, and hardness (it won't be scratched by a steel knife). Commonly found in areas with ancient volcanic activity such as Arizona (USA), Madagascar, and Indonesia.