sedimentary

Chert (likely flint-bearing chert)

Microcrystalline quartz, SiO₂ (chalcedony/quartz aggregate)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; gray to brown, opaque, with dull to waxy luster and conchoidal fracture. Very fine-grained, lacks visible crystals or cleavage; the pale, weathered surface and darker fresh break are typical.

Identified August 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms mainly by silica replacement of limestone or from siliceous sediment accumulation, commonly during the Paleozoic–Mesozoic. Exact age and subtype cannot be determined from the image alone.

Uses & applications

Used historically for sharp-edged tools, arrowheads, and fire-starting; today it is mainly a lapidary, teaching, and collector material, with limited aggregate use.

Geological facts

Fresh chert breaks into sharp conchoidal edges and may preserve fossils or subtle banding. Flint is a dark, often nodular variety of chert, especially associated with chalk.

Field identification & locations

Identify it by testing for glass-like conchoidal fracture, lack of visible grains, and inability to scratch it with a steel knife; quartz should scratch glass. Common in limestone and chalk regions worldwide; this specimen’s rough triangular form may be naturally fractured or tool-worked.