sedimentary

Banded chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert/flint with pale silica bands

AI-generated identification · may be incorrect

Hardness about 7 Mohs; waxy to dull luster, opaque gray-black and cream-white banding, very fine-grained cryptocrystalline structure, and no visible cleavage. It typically breaks with a curved conchoidal fracture and has specific gravity near 2.6.

Identified August 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or cement sediment, commonly from marine biological silica, during diagenesis; the contrasting bands reflect changes in impurities or depositional conditions. Exact age cannot be determined from the image.

Uses & applications

Used historically for sharp tools and fire-starting, and today as a lapidary, ornamental, and teaching material; this small irregular piece has little commercial value.

Geological facts

Flint is a dark, tough variety of chert, while lighter bands may contain chalcedony or quartz. The specimen appears naturally weathered or possibly partly polished.

Field identification & locations

Identify it by its very fine texture, glassy/waxy surface, hardness, and sharp conchoidal chips; it commonly occurs in limestone regions, river gravels, and glacial deposits. A steel file should not easily scratch it.