sedimentary

Chert (Flint)

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, brown, or black (often mottled); Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (exhibits conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Gray, brown, or black (often mottled)
Luster: Waxy to dull

Identified April 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 from groundwater. Often found as nodules within limestone or chalk beds, typically dating from the Paleozoic or Mesozoic eras.

Uses & applications

Historically used for stone tools (arrowheads, knives) and sparking fire. Currently used in road surfacing, decorative landscaping, and occasionally as a low-cost gemstone when polished.

Geological facts

Flint was the primary 'high-tech' material of the Stone Age due to its ability to produce razor-sharp edges. It is famous for its use in flintlock firearms to ignite gunpowder.

Field identification & locations

Identify in the field by its waxy texture and distinctive shell-like (conchoidal) fractures. It is commonly found in gravel pits, riverbeds, or embedded in carbonate rocks. It is harder than steel and will easily scratch glass.