sedimentary

Chert (Flint Nodules)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Gray, black, tan, or brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: Gray, black, tan, or brown
Luster: Waxy to dull

Identified June 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation within limestone or chalk beds. Often Cretaceous in age.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, as a gemstone (jasper/agate varieties), and as flint for fire-starting.

Geological facts

Chert was one of the most important minerals for prehistoric humans due to its ability to be knapped into sharp edges. It is chemically identical to quartz but has a different microscopic structure.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and inability to be scratched by a steel pocketknife. Common in limestone outcrops and riverbeds.