sedimentary

Chert (Flint variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Dark grey to brown with tan cortex, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Identified April 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of siliceous remains of organisms (like diatoms or radiolarians) or chemical precipitation in sedimentary environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used for decorative stone, industrial grinding media, and as a component in certain ceramics.

Geological facts

Flint was one of the first materials harvested by early humans. It is famous for its ability to create sparks when struck against steel, a property used for centuries to start fires and fire muskets.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and sharp edges. It can scratch glass. Often has a lighter-colored weathered outer 'skin' or cortex.