sedimentary

Flint (chert) fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark

AI-generated identification · may be incorrect

A small, angular gray-brown fragment with a smooth, curved fracture surface, consistent with conchoidal fracture. Chert is typically Mohs 7, vitreous to waxy, and has no cleavage; the image does not reveal its internal texture clearly.

Identified October 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates and replaces material in sedimentary rocks, often limestone or chalk. Its age depends on the host formation and cannot be determined from the image.

Uses & applications

Flint has historically been used for tools and fire-starting; chert is also collected and occasionally used as decorative stone.

Geological facts

Sharp conchoidal edges made flint valuable for prehistoric cutting tools and projectile points.

Field identification & locations

Look for hard, fine-grained material that can scratch glass and breaks into curved, sharp-edged surfaces; it occurs worldwide in sedimentary deposits. This small fragment has little commercial value, approximately $0–$5.