sedimentary

Flint or chert fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark and nodular

AI-generated identification · may be incorrect

Typically gray to brown, waxy or dull luster, very fine-grained with conchoidal fracture; hardness about 7 Mohs, no cleavage, and specific gravity around 2.6. The specimen appears weathered and possibly coated with iron-oxide staining.

Identified September 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms by precipitation or replacement of silica in marine limestone and chalk, commonly during the Cretaceous or other sedimentary periods. Exact age cannot be determined from the photograph.

Uses & applications

Used historically for stone tools, fire-starting, and construction aggregate; attractive polished pieces may be collected, but this rough fragment has little commercial value.

Geological facts

Flint is a dense variety of chert whose sharp conchoidal edges were valuable to prehistoric toolmakers. Freshly broken surfaces are usually smoother and more glass-like than weathered exteriors.

Field identification & locations

Identify with a glass-scratch test: genuine chert scratches glass, though many materials do also; inspect for conchoidal fracture and a non-crystalline appearance. Common in chalk, limestone, and sedimentary gravel deposits worldwide.