fossil

Petrified Wood

Silicified Wood (SiO2 permineralization)

Hardness: 6.5-7 on the Mohs scale. Color: Brown, dark grey, black, and tan. Luster: Vitreous to dull. Crystal Structure: Microcrystalline (Quartz/Chalcedony replacing organic plant tissue). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.8.

Hardness: 6
Color: Brown, dark grey, black, and tan
Luster: Vitreous to dull

Identified July 26, 2026More fossil →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic plant material (tree trunk or branch) was rapidly buried under sediment or volcanic ash, excluding oxygen. Silica-rich groundwater passed through the plant matter, replacing the organic cell walls with minerals over millions of years, commonly during the Mesozoic or Cenozoic eras.

Uses & applications

Used primarily for display specimens, lapidary work, decorative carvings, bookends, jewelry, and educational collections.

Geological facts

Petrified wood preserves the original cellular structure of the tree down to a microscopic level, allowing paleobotanists to identify the species of tree that lived tens to hundreds of millions of years ago.

Field identification & locations

Identify in the field by looking for fibrous, wood-like ring or grain textures combined with the weight and hardness of stone. Found widely in areas with ancient sedimentary or volcanic deposits, such as the western United States, Madagascar, and Indonesia.

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