sedimentary

Banded chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert with a pale weathered/altered zone

AI-generated identification · may be incorrect

Typically hardness 6.5–7, waxy to dull luster, opaque, very fine-grained and non-cleavable; colors range from dark gray-blue to cream. The specimen appears water-rounded, with contrasting silica-rich bands or zones and minor surface pits.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when microcrystalline quartz replaces or precipitates from silica-rich marine sediments, commonly during the Paleozoic–Cenozoic; this pebble was later eroded and rounded in a river, beach, or glacial deposit. Exact age and composition require testing.

Uses & applications

Used historically for sharp tools and fire-starting, and sometimes as decorative aggregate or lapidary material; this small common pebble has little commercial value.

Geological facts

Fresh chert breaks with a smooth conchoidal fracture and can produce razor-sharp edges. The cream area may represent weathering, recrystallization, or a different sedimentary silica layer rather than a separate rock.

Field identification & locations

Identify by its glassy-to-waxy fracture, high hardness, lack of visible grains, and inability to scratch with a steel nail; it should scratch ordinary glass. Common in limestone terrains, gravel beds, beaches, and glacial deposits.