sedimentary

Weathered chert (flint) pebble

Microcrystalline quartz (SiO₂), likely chert

AI-generated identification · may be incorrect

Fine-grained, dull gray-green center with a yellow-brown weathered rind and dark patches; quartz hardness about 7 Mohs, no visible crystals, and conchoidal fracture when freshly broken. The rounded shape and smooth surface suggest water or beach abrasion.

Identified September 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica accumulates and recrystallizes in sedimentary settings, often replacing carbonate sediments; its age cannot be determined from the photograph. Weathering has altered the exterior, while transport likely rounded the pebble.

Uses & applications

Chert has historically been used for sharp-edged tools and fire-starting; attractive pieces may be collected or used decoratively.

Geological facts

Flint is a variety of chert, and fresh fractures can produce very sharp edges. The image shows a small rounded specimen rather than enough diagnostic detail to distinguish chert confidently from other fine-grained stones.

Field identification & locations

Look for a waxy-to-dull surface, very fine texture, and curved, shell-like fracture; common in sedimentary deposits and gravel beaches. Avoid identifying it solely by the weathered rind.