sedimentary

Banded Chert (Flint)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Black with grey or white bands; Luster: Waxy to dull; Crystal structure: Microcrystalline (cryptocrystalline); Fracture: Conchoidal; Specific gravity: 2.6-2.7

Hardness: 6
Color: Black with grey or white bands
Luster: Waxy to dull

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Black with grey or white bands; Luster: Waxy to dull; Crystal structure: Microcrystalline (cryptocrystalline); Fracture: Conchoidal; Specific gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. The banding represents changes in sediment composition over time, often during the Precambrian to Paleozoic eras.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in lapidary arts, jewelry, as decorative stones, and in the production of fire-striking tools.

Geological facts

This specimen is a water-worn or tumbled pebble showing distinct layering. Chert is extremely durable and weather-resistant, which is why it is often found as smooth river stones long after the surrounding rock has eroded.

Field identification & locations

Identify by its parallel banding, waxy texture, and conchoidal fracture. Commonly found in riverbeds, glacial tills, and coastal beaches where sedimentary limestone or chalk once existed.