mineral

Chert or chalcedony nodule

Microcrystalline quartz (SiO₂), possibly weathered chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pale gray to white, with a dull-to-waxy luster and irregular conchoidal fracture. The granular, weathered surface and translucent gray edge are consistent with microcrystalline quartz, though the photo does not resolve exact texture.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica precipitated from groundwater or replaced material in sedimentary rock, commonly during the Paleozoic–Cenozoic; precise age and locality require context or testing.

Uses & applications

Used for flaked tools, abrasives, aggregate, and decorative specimens; attractive translucent pieces may be polished, but this specimen appears mainly of modest collecting interest.

Geological facts

Chert and chalcedony are quartz varieties distinguished by crystal size: chert is generally opaque and granular, while chalcedony is more translucent and fibrous. Similar-looking white material can also be quartz-rich limestone or weathered slag.

Field identification & locations

Check for a glassy/conchoidal fracture, inability to scratch it with a steel knife, and lack of fizz in dilute hydrochloric acid; acid fizz would suggest carbonate rock. Common in sedimentary formations, gravel beds, and eroded outcrops.