sedimentary

Chert (flint)

Microcrystalline quartz (SiO₂), commonly called chert; flint is a dark variety

AI-generated identification · may be incorrect

Pale gray-beige, opaque, with a dull to waxy luster and irregular, sharp conchoidal fracture. Hardness is about 7 Mohs; crystals are microscopic and not visible.

Identified October 16, 2026More sedimentary →

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Physical properties

Pale gray-beige, opaque, with a dull to waxy luster and irregular, sharp conchoidal fracture. Hardness is about 7 Mohs; crystals are microscopic and not visible.

Formation & geological history

Forms when silica accumulates and hardens in sedimentary settings, often replacing carbonate sediment. Its age cannot be determined from the image and varies widely by deposit.

Uses & applications

Used historically for cutting tools and fire-starting; today it is mainly collected or used as decorative stone.

Geological facts

Chert can break into exceptionally sharp edges, making it an important material for prehistoric tools.

Field identification & locations

The angular shape and smooth, curved fracture surfaces are consistent with chert, but visual identification is uncertain. It occurs in sedimentary formations worldwide; inspect a fresh edge for a glassy, shell-like fracture.