sedimentary

Chert (flint), likely a weathered nodule fragment

Microcrystalline quartz (SiO₂), commonly termed chert or flint

AI-generated identification · may be incorrect

Hardness about 7 Mohs; tan to brown, dull to waxy luster, very fine-grained with no visible crystals or cleavage. The angular piece has a pale weathered surface; a fresh break may be glassy and conchoidal.

Identified October 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica precipitates or replaces sediment in marine or lake deposits, often during diagenesis. Chert occurs in rocks of many ages, from ancient formations to recent deposits.

Uses & applications

Historically used for tools and fire-starting; today used for decorative stone, aggregates, and collecting.

Geological facts

Chert’s sharp conchoidal fractures made it valuable for prehistoric blades and arrowheads.

Field identification & locations

Look for a dense, hard, fine-grained stone that scratches glass and breaks with curved, sharp edges; common in sedimentary formations and gravel deposits worldwide. The photo alone cannot confirm the exact variety.