sedimentary

Rounded brown chert or flint pebble

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown to gray, dull-to-waxy luster, very fine-grained and opaque to slightly translucent. It lacks visible cleavage and typically shows smooth conchoidal fracture; the rounded shape indicates water abrasion.

Identified September 15, 2026More sedimentary →

Explore Rounded brown 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

Forms when silica-rich groundwater replaces or fills pores in sedimentary rocks, commonly limestone or chalk, during diagenesis. The specimen’s exact geological age cannot be determined visually; later stream or beach transport rounded it.

Uses & applications

Used historically for flint tools and fire-starting, and today as decorative stone, lapidary material, aggregate, or a minor gemstone. Small common pebbles have little commercial value.

Geological facts

Chert and flint are compositionally similar varieties of microcrystalline quartz; “flint” often refers to dark chert associated with chalk. It can produce a sharp edge when fractured.

Field identification & locations

Identify by its hardness, waxy texture, lack of grains, and conchoidal fracture; it should scratch glass but not be scratched by a steel knife. Common in limestone regions, river gravels, beaches, and glacial deposits.