sedimentary

Chert or flint fragment

Microcrystalline quartz (SiO₂), often with chalcedony

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, dull to waxy luster, fine-grained and opaque to translucent; commonly gray, cream, brown, or red. It has no visible crystals or cleavage and breaks with smooth, curved conchoidal fracture, producing sharp edges.

Identified August 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediment, commonly in limestone and chalk; deposits range from Precambrian to recent geological ages. The fragment’s pale color may reflect silica-rich composition or weathering.

Uses & applications

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

Geological facts

Flint is a dark variety of chert, while chert includes lighter varieties. Freshly fractured surfaces can be extremely sharp and may spark against steel.

Field identification & locations

Look for a waxy surface, very fine texture, lack of cleavage, and conchoidal fracture; it should scratch ordinary glass. Common in limestone regions, including parts of Europe, North America, and the Middle East.