fossil

Agatized fossil nodule, possibly silicified wood or bone

Microcrystalline quartz (chalcedony), SiO₂, replacing fossil material

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, translucent chalcedony core with a rough tan, porous rind. Waxy to dull luster, cryptocrystalline structure, and no obvious cleavage; the texture suggests a fossilized or silicified organic nodule rather than ordinary agate.

Identified August 21, 2026More fossil →

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Physical properties

Formation & geological history

Silica-rich groundwater gradually replaced or filled an organic structure, commonly during burial in volcanic ash or sediment. Exact age and identity cannot be determined from the photograph; specimens of this type range from Paleozoic to Cenozoic.

Uses & applications

Primarily a collector specimen, cabochon, or lapidary material; chalcedony is also used for carvings and jewelry. The porous rind is usually trimmed or preserved for display.

Geological facts

The smooth translucent interior and contrasting weathered rind are characteristic of silicification. Internal texture, pores, growth lines, or cellular patterns would be needed to distinguish silicified wood, bone, or another fossil.

Field identification & locations

Commonly found in volcanic-sedimentary terrains and arid gravel deposits, especially in the western United States, Madagascar, and Australia. It scratches glass but should not be scratched by a steel knife; acid typically produces no reaction.