sedimentary

Likely flint (chert) fragment

Microcrystalline quartz (SiO₂), commonly called chert or flint

AI-generated identification · may be incorrect

The small angular fragment has a dark, smooth-looking body and tan weathered areas, consistent with fractured chert; exact hardness, luster, and density cannot be confirmed from the image. Chert is typically Mohs 6.5–7, with a waxy to dull luster and no cleavage; its crystals are too fine to see unaided.

Identified September 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica accumulates and replaces material in sedimentary deposits, often as nodules in limestone or chalk. Chert occurs across many geological ages.

Uses & applications

Used historically for sharp tools and fire-starting; today it is mainly collected, and some varieties are used as decorative stone.

Geological facts

Chert breaks with a curved, conchoidal fracture that can produce very sharp edges.

Field identification & locations

Look for a hard, fine-grained texture, conchoidal fracture, and edges that may be translucent; the pictured fragment is suggestive, but not diagnostic. Chert is widespread worldwide in sedimentary formations.