sedimentary

Flint (chert)

Microcrystalline quartz (SiO₂), commonly called flint when dark-colored

AI-generated identification · may be incorrect

Dense, dark gray to black, with a dull-to-waxy luster and irregular to conchoidal fracture; hardness about 7 Mohs. The fine-grained quartz crystals are too small to see individually; cleavage is absent.

Identified October 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates and replaces material in sedimentary rocks, especially limestone and chalk. Specimen age cannot be determined from the image; flint commonly occurs in sedimentary deposits of many geological ages.

Uses & applications

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

Geological facts

A sharp conchoidal fracture can produce exceptionally keen edges, making flint important in prehistoric toolmaking.

Field identification & locations

Look for a hard, compact, dark stone with curved fracture surfaces and sometimes a pale weathered outer rind; common in chalk and limestone regions, including southern England and parts of Europe. Exact identification from the image alone is not certain.