sedimentary

Chert (Quartz Variety)

Silicon Dioxide (SiO2)

Hardness: 7; Color: Tan, brown, or white; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchonidial fracture); Specific Gravity: 2.65

Hardness: 7
Color: Tan, brown, or white
Luster: Waxy to dull

Identified June 6, 2026More sedimentary →

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Physical properties

Hardness: 7; Color: Tan, brown, or white; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchonidial fracture); Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich microfossils like sponge spicules or radiolarians, or via chemical precipitation in carbonate environments. Prevalent in ancient seabed deposits.

Uses & applications

Historically used for making tools and arrowheads. Currently used as road construction material, decorative stone, and in glass manufacturing.

Geological facts

Flint is a variety of chert. It was one of the most important first materials for early humans because its conchoidal fracture allows it to produce extremely sharp edges.

Field identification & locations

Look for a microcrystalline texture that is too hard to be scratched by a steel blade. It often forms as nodules or layered beds within limestone or chalk. Commonly found in riverbeds and limestone outcrops.