sedimentary

Likely brown chert (flint) pebble

Microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Opaque, brown, rounded and weathered, with a dull to waxy surface; quartz has Mohs hardness 7 and trigonal crystal structure, though crystals are microscopic. The image does not reveal a diagnostic fracture or test hardness, so identification is provisional.

Identified October 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica precipitates or replaces material in sedimentary settings, often in limestone or chalk; its age varies widely by deposit. This rounded shape suggests natural abrasion during transport.

Uses & applications

Chert has been used for tools and striking sparks; attractive pieces are collected, but this specimen appears small and unworked.

Geological facts

Fresh chert commonly breaks with a curved, shell-like (conchoidal) fracture and sharp edges.

Field identification & locations

Look for hardness sufficient to scratch glass and a conchoidal fracture; common in sedimentary rocks and river or beach gravels worldwide. A photograph alone cannot confirm the identification.