sedimentary

Likely chert (flint) fragment

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Brown-gray, opaque to slightly translucent edges, with a dull to waxy luster and curved/conchoidal fracture surfaces. Mohs hardness about 7; no visible crystals or cleavage. Identification from the photo is tentative.

Identified October 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica precipitates or accumulates in sediment and later lithifies; it occurs in rocks of many geological ages, often as nodules in limestone or chalk.

Uses & applications

Used historically for tools and fire-starting; today it is mainly collected, or used decoratively and as aggregate.

Geological facts

Its sharp, curved fracture edges made chert valuable for prehistoric cutting tools.

Field identification & locations

Look for hardness that scratches glass, a waxy surface, and shell-like fracture; common worldwide in sedimentary formations. The pictured small, rough fragment has little commercial value.