sedimentary

Flint or chert flake

Microcrystalline quartz (SiO₂), commonly chalcedony with possible minor impurities

AI-generated identification · may be incorrect

Very fine-grained, dark brown-gray, dull to waxy luster, conchoidal fracture, no visible crystals or cleavage; Mohs hardness about 6.5–7. The sharp triangular form and flake scars suggest intentional knapping or natural fracture.

Identified September 21, 2026More sedimentary →

Explore Flint or chert flake 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

Chert forms when silica replaces or fills pores in sedimentary rocks, often marine limestone, during diagenesis; its age depends on the host formation. This specimen appears cut or knapped, possibly an archaeological stone tool fragment, but the image alone cannot confirm human manufacture.

Uses & applications

Chert is used historically for blades, arrowheads, fire-starting tools, and occasionally aggregate or decorative stone. A confirmed artifact may have archaeological value, while ordinary flakes are inexpensive.

Geological facts

Edges can become extremely sharp because conchoidal fracture produces thin, acute margins. Dark coloration commonly results from organic matter, iron, or manganese impurities.

Field identification & locations

Identify by hardness, glass-like conchoidal fracture, and inability to scratch it with a steel knife; it should scratch glass. Common in sedimentary terrains worldwide, especially limestone regions.