sedimentary

Banded chert or flint pebble

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark gray to black with cream/tan weathering bands, waxy to dull luster, and no visible crystals or cleavage. It appears naturally water-rounded and may show conchoidal fracture.

Identified September 8, 2026More sedimentary →

Explore Banded chert or flint pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed when silica-rich fluids replaced or cemented fine sediment, commonly during the Paleozoic–Mesozoic in marine limestone or chalk; later erosion produced the rounded pebble. Exact age and locality cannot be determined from the image.

Uses & applications

Used historically for sharp tools and fire-starting, and today for lapidary carvings, cabochons, landscaping, and geological collections; ordinary pebbles have modest commercial value.

Geological facts

Chert and flint are compositionally similar varieties of microcrystalline quartz; darker color often reflects organic matter or iron/manganese impurities. Cream-colored veins may be silica, carbonate, or surface weathering.

Field identification & locations

Identify it by its very high hardness, glassy or waxy appearance, lack of cleavage, and conchoidal breaks; it should scratch glass. Common in river gravels, limestone regions, and glacial deposits.