sedimentary

Flint (chert)

Microcrystalline quartz (SiO₂), a variety of chert

AI-generated identification · may be incorrect

Dense, fine-grained stone with gray, cream, and brown areas and a dull to waxy luster; hardness about 7 Mohs. It commonly fractures with smooth, curved, sharp-edged surfaces; crystal structure is too fine to see unaided.

Identified October 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates and replaces material in sedimentary rocks, often as nodules in limestone or chalk. It can form in many geological periods; the specimen’s age cannot be determined from the image.

Uses & applications

Historically used for tools, scrapers, and fire-starting; today collected and occasionally used for knapping or decorative objects.

Geological facts

Flint is a form of chert prized for conchoidal fracture, which produces sharp edges. The image shows a rough, irregular fragment, but no diagnostic features establish its exact source.

Field identification & locations

Look for a very hard, fine-grained stone that resists scratching by steel and breaks into curved, sharp-edged flakes. Chert occurs worldwide in sedimentary formations; this small common fragment has an estimated value of $1–$10.