sedimentary

Flint (chert), possibly worked

Microcrystalline quartz; SiO₂ (chalcedony/quartz aggregate)

AI-generated identification · may be incorrect

Typically dark gray to black, brown-weathering, with waxy to dull luster and conchoidal fracture; Mohs hardness about 6.5–7, no cleavage, and specific gravity about 2.6. The sharp edges and repeated flake scars suggest intentional prehistoric knapping, though natural breakage is also possible.

Identified August 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Flint forms when silica-rich groundwater replaces carbonate sediments, commonly in Cretaceous and younger marine chalk or limestone. The specimen’s geological age cannot be determined from the image; its apparent shaping may be much younger than the host rock.

Uses & applications

Historically used for stone tools, projectile points, scrapers, and fire-starting; today it is mainly a teaching or archaeological collectible. Quality flint is occasionally used decoratively, but it has little commercial value.

Geological facts

Conchoidal fracture produces exceptionally sharp edges, making flint important in prehistoric technology. The lighter gray outer rind may represent weathered cortex or alteration.

Field identification & locations

Identify it by its dense uniform texture, glassy/waxy appearance, lack of visible grains, and curved fracture surfaces; a magnifier may reveal tiny fossils or inclusions. Common in chalk and limestone regions worldwide, including England, France, the American Midwest, and Texas.