sedimentary

Dark brown flint/chert fragment

Microcrystalline quartz (SiO₂), often with minor chalcedony and impurities

AI-generated identification · may be incorrect

Hardness ~6.5–7 Mohs; dark brown to black, dull to waxy luster, very fine-grained and non-cleavable. It breaks with sharp conchoidal edges and has a typical specific gravity near 2.6.

Identified August 16, 2026More sedimentary →

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Physical properties

Hardness ~6.5–7 Mohs; dark brown to black, dull to waxy luster, very fine-grained and non-cleavable. It breaks with sharp conchoidal edges and has a typical specific gravity near 2.6.

Formation & geological history

Chert forms when silica-rich groundwater replaces or fills pore spaces in sediment, commonly limestone or chalk; the brown color reflects iron and organic impurities. Formation ages vary widely, from Paleozoic to Cenozoic.

Uses & applications

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

Geological facts

Its conchoidal fracture can produce extremely sharp edges, making flint technologically important to prehistoric cultures. The specimen’s rough, irregular form is consistent with a naturally broken fragment.

Field identification & locations

Identify it by testing for glass-scratching hardness, observing waxy luster, and checking for conchoidal fracture; it commonly occurs in chalk, limestone, and gravel deposits worldwide. Exact identification is limited by the photograph.