sedimentary

Yellow-brown chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert; exact identification is uncertain from the image alone

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan to mustard-brown, dull to waxy luster, very fine-grained cryptocrystalline structure, no visible cleavage, and conchoidal fracture may appear on broken edges. The rounded shape and surface smoothing indicate water transport or tumbling.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or cement carbonate sediment, commonly during the Paleozoic–Cenozoic eras; this specimen was likely weathered from bedrock and rounded in a stream or gravel deposit.

Uses & applications

Common chert is used historically for tools and fire-starting, and occasionally as aggregate or landscaping stone; attractive pieces are collected but are generally not gem-grade.

Geological facts

Its apparent yellow color can result from iron-oxide staining, clay, or other inclusions. It may resemble jasper, but chert is typically more uniformly microcrystalline and translucent at thin edges.

Field identification & locations

Look for a glassy or waxy surface, very high scratch resistance, and conchoidal chips; it should scratch ordinary glass but not be scratched by a steel knife. Commonly found in limestone regions, river gravels, and glacial deposits.