Sedimentary / Fossil

Petrified Wood

Fossilized wood / Silicified wood

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish, grey, yellow, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz (chalcedony/opal/agate replacing wood), Cleavage: None (conchoidal fracture), Specific gravity: 2.58-2.91

Hardness: 6

Identified June 9, 2026More sedimentary / fossil →

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Physical properties

Formation & geological history

Formed when plant material is buried by sediment and protected from decay due to oxygen deprivation. Groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, pyrite, or another inorganic material such as opal.

Uses & applications

Used in lapidary arts, jewelry, collecting, interior decor, and scientific study of paleoenvironments.

Geological facts

Petrified wood can preserve the original cell structure of the wood down to the microscopic level. Famous locations include the Petrified Forest National Park in Arizona.

Field identification & locations

Identify by looking for wood-like grain and bark textures that are heavy and hard like stone. Often found in sedimentary rock formations, especially those related to ancient floodplains or volcanic ash deposits.

Other sedimentary / fossil specimens

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Chalcedony (Tumbled)

Silicon Dioxide (SiO2)

mineral

Coral Fossil (Agatized Coral or Petoskey Stone)

Hexagonaria percarinata (if Petoskey) or generally Scleractinia (Agatized Coral)

Sedimentary/Fossil

Fossilized Coral

Anthozoa (Fossilized)

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Trilobite Pygidium (Tail Segment)

Phylum Arthropoda, Class Trilobita (likely order Phacopida)

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Fossilized Shark Tooth (Otodus obliquus)

Otodus obliquus (Mineral composition: Bio-apatite/Calcium Phosphate replaced by various minerals)

sedimentary (fossil)

Fossilized Sea Urchin (Echinoid)

Echinoidea (Class); commonly Clypeasteroida for sand dollar types

sedimentary (fossil)