sedimentary

Worked chert (likely flint)

Microcrystalline quartz/chalcedony, SiO₂

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown to tan, waxy or dull luster, very fine-grained and opaque to slightly translucent. It shows conchoidal fracture and sharp flake scars; no visible cleavage or crystals.

Identified August 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich groundwater replaces or accumulates within sedimentary rocks, commonly limestone, during diagenesis. The flaked edges indicate human knapping, but the geological material may range from Paleozoic to Cenozoic in age depending on its source.

Uses & applications

Used historically for stone tools, arrowheads, fire-starting, and cutting edges; attractive varieties are occasionally sold as lapidary material. This small worked fragment has modest commercial value.

Geological facts

The pale gray-green patches may be weathered cortex, mineral alteration, or a different silica-rich zone. Its sharp, curved flake scars are characteristic of knappable chert rather than ordinary sandstone.

Field identification & locations

Identify it by its glassy conchoidal fracture, lack of grains, high hardness, and inability to scratch with a steel knife; it should scratch glass. Common sources include limestone terrains worldwide, especially Europe and North America.