sedimentary

Likely chert or weathered flint fragment

Microcrystalline quartz (SiO₂), possibly chalcedony-rich chert

AI-generated identification · may be incorrect

Gray-brown, dull to slightly waxy luster; very fine-grained with no visible crystals or cleavage. Hardness about 6.5–7 Mohs, specific gravity roughly 2.6; the pointed shape may result from conchoidal fracture or natural weathering.

Identified September 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich groundwater replaces or fills sediment, commonly in limestone or chalk, during diagenesis; its age depends on the host formation. This specimen may also be a worked or naturally fractured flake.

Uses & applications

Used historically for cutting tools, arrowheads, and fire-starting; attractive varieties are collected, but ordinary fragments have little commercial use.

Geological facts

Fresh chert fractures with sharp, curved edges and can scratch glass. Flint is a dark, especially dense variety of chert, while chalcedony is its more translucent fibrous form.

Field identification & locations

Common in sedimentary terrains, especially limestone regions, river gravels, and glacial deposits. Look for a glassy waxy fracture, lack of visible grains, and inability to scratch it with a steel knife.