sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

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

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

Identified May 24, 2026More sedimentary →

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Physical properties

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

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or by chemical precipitation in marine or groundwater environments.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) and starting fires. Today used as road surfacing material or for decorative landscaping.

Geological facts

Flint is a variety of chert that was essential to human survival for thousands of years due to its ability to produce sharp edges and create sparks when struck against steel.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and extreme hardness (it will scratch glass). Often found as nodules within limestone or chalk beds.