sedimentary

Chert (Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: light gray to white with tan weathering; Luster: waxy to dull; Structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: light gray to white with tan weathering
Luster: waxy to dull

Identified April 7, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 on Mohs scale; Color: light gray to white with tan weathering; Luster: waxy to dull; Structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed by the precipitation of silica in sedimentary environments, often replacing carbonate material (limestone) or as nodules. Often originating from the accumulation of microscopic silica-walled organisms.

Uses & applications

Historically used for making stone tools (arrowheads, knives) due to its sharp edges; used in construction aggregates, road beds, and occasionally as an industrial grinding medium.

Geological facts

Chert and flint were essential to early human survival for tool making and starting fires. It is so tough that it was often used as ballast in historical ships.

Field identification & locations

Identify in the field by its characteristic smooth, bowl-shaped 'conchoidal' fractures and its ability to scratch glass or steel. Found globally in limestone and chalk deposits.