sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: tan, grey, brown, white; Luster: waxy to dull; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: none; Fracture: Conchoidal (shell-like curves); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale), Color: tan, grey, brown, white
Color: tan, grey, brown, white
Luster: waxy to dull

Identified May 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in sedimentary environments. Common in limestone and chalk beds.

Uses & applications

Historically used for stone tools (knapping) and fire-starting. Currently used in road construction, as jewelry (if colorful), and as an abrasive.

Geological facts

Chert was one of the most important materials for early humans because its conchoidal fracture creates extremely sharp edges for hunting and scraping. It is chemically very resistant to weathering.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, waxy surface with curved fracture edges. Commonly found in riverbeds and limestone outcrops.