sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 Mohs
Color: Grey, brown, or tan
Luster: Waxy to dull

Identified May 22, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Forms in sedimentary environments, often as nodules within limestone or chalk through the replacement of calcium carbonate by silica-rich fluids. Can be of various ages from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads, knives); currently used in road surfacing, as grinding media in ceramic mills, and as a starting material for fire-making (flint and steel).

Geological facts

Flint was one of the first materials exploited by early humans due to its ability to break with sharp, predictable edges. It is often found with a white 'cortex' or weathered outer rind.

Field identification & locations

Identify by its extremely sharp edges when broken, waxy texture on fresh surfaces, and smooth curved (conchoidal) fracture lines. Commonly found in riverbeds or within chalk cliffs.