sedimentary

Weathered dark flint (chert) pebble

Microcrystalline quartz (SiO₂), commonly called flint or chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark gray-brown, dull to waxy luster, extremely fine-grained and non-cleavable. The pale, rough edge likely exposes a weathered cortex or fresh fracture; shape appears water-rounded and possibly polished.

Identified August 8, 2026More sedimentary →

Explore Weathered dark flint (chert) 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

Forms when silica replaces or accumulates within marine carbonate sediments, often during the Cretaceous or other sedimentary periods; its exact age cannot be determined from the image. Rounded examples are commonly transported in rivers, beaches, and glacial gravels.

Uses & applications

Used historically for sharp-edged tools and fire-starting, and today mainly as a lapidary, decorative, or teaching specimen; it has little industrial value in pebble form.

Geological facts

Flint is a dense variety of chert that can produce a conchoidal fracture and very sharp edges. Dark coloration commonly comes from organic matter, iron, or other trace impurities.

Field identification & locations

Identify by its opaque dark body, waxy feel, high hardness, and conchoidal fracture; it should scratch glass but not be scratched by a steel knife. Common in chalk and limestone regions, including England, France, Scandinavia, and many gravel deposits worldwide.