fossil

Petrified Wood

Silicified wood (SiO2)

Hardness of 7 on the Mohs scale, vitreous to dull luster, and preserves cellular wood structure with multicolored quartz composition.

Identified October 18, 2026More fossil →

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Physical properties

Hardness of 7 on the Mohs scale, vitreous to dull luster, and preserves cellular wood structure with multicolored quartz composition.

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

Used in ornamental carving, jewelry, lapidary art, and sought after by fossil and rock collectors.

Famous occurrences include the Petrified Forest National Park in Arizona, featuring logs dating back over 200 million years.

Identify by retaining wood grain patterns while feeling unusually heavy and exhibiting conchoidal fracture 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)