sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Tan, brown, or grey; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 7 Mohs
Color: Tan, brown, or grey
Luster: Dull to waxy

Identified April 11, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Tan, brown, or grey; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed in marine environments through the accumulation of silica-rich microfossils or via chemical precipitation in limestone or chalk beds.

Uses & applications

Used historically for stone tools (arrowheads), as a fire-starter, in decorative landscaping, and as a component in road base or abrasive grit.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most vital materials for early humans because its conchoidal fracture creates razor-sharp edges.

Field identification & locations

Identify by its 'glassy' smooth texture when broken and its characteristic bowl-shaped (conchoidal) fractures. Found frequently in riverbeds or within limestone outcrops.