fossil

Petrified Wood

Silicified Wood (Quartz replacement of organic wood)

Hardness of 7 on the Mohs scale, exhibits brown, gray, and black wood-grain patterns, vitreous to waxy luster, and cryptocrystalline structure.

Identified October 18, 2026More fossil →

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Physical properties

Hardness of 7 on the Mohs scale, exhibits brown, gray, and black wood-grain patterns, vitreous to waxy luster, and cryptocrystalline structure.

Formed through permineralization when buried organic wood is slowly replaced by silica-rich groundwater over millions of years.

Used for decorative items, jewelry, lapidary art, and sought after by fossil and rock collectors.

Famous occurrences include the Petrified Forest National Park in Arizona, containing trees dating back over 200 million years to the Triassic period.

Identified by retaining original cellular wood structures and tree rings while possessing the extreme hardness and weight of quartz.

Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

Fossiliferous limestone (likely a crinoidal or shell-fragment limestone)

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

Porous limestone pebble

Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image

Fossil oyster shell

Oyster (family Ostreidae); shell composed chiefly of calcite (CaCO₃)