sedimentary

Chert or flint fragment

Microcrystalline quartz (SiO₂), likely chert

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, waxy to dull luster, opaque gray-brown color, very fine-grained cryptocrystalline structure, and no visible cleavage; it breaks with curved conchoidal fractures and sharp edges. The specimen appears weathered and possibly naturally shaped or worked.

Identified August 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich groundwater replaces or accumulates within limestone, commonly from microscopic marine organisms; many examples range from Paleozoic to Cenozoic age. This piece may be a flake or fragment from a larger nodule.

Uses & applications

Used historically for cutting tools, arrowheads, fire-starting, and occasionally as aggregate or decorative stone. It has little jewelry value unless unusually colored, patterned, or expertly knapped.

Geological facts

Chert and flint are varieties of microcrystalline quartz; “flint” commonly refers to dark chert associated with chalk. Sharp conchoidal edges are a key diagnostic feature.

Field identification & locations

Look for glassy or waxy surfaces, extreme hardness, inability to scratch it with a steel knife, and conchoidal fracture; it commonly occurs in limestone, chalk, river gravels, and glacial deposits. Exact identification is uncertain from the image alone.