sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness 7 on Mohs scale; waxy to vitreous luster; translucent to opaque gray, tan, and brown color; conchoidal fracture with sharp edges; specific gravity around 2.58–2.64; cryptocrystalline quartz crystal structure.

Identified November 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through biochemical and chemical precipitation of microcrystalline silica, typically within marine sedimentary deposits like chalk, limestone, or marl, often as diagenetic replacement nodules during the Phanerozoic eon.

Uses & applications

Historically used in prehistoric stone toolmaking (arrowheads, blades, scrapers) and strike-a-light flintlocks; modernly used as industrial abrasives, road aggregate, and semi-precious material for lapidary and cabochons.

Geological facts

Due to its predictable, glass-like conchoidal fracture, flint was essential to early human development during the Stone Age. When struck against iron or steel, it produces hot sparks capable of igniting tinder.

Field identification & locations

Recognized in the field by its smooth, waxy feel, flinty conchoidal fractures, sharp edges when broken, and outer weathered chalky or iron-stained cortex. Commonly found in limestone quarries, chalk cliffs, gravel beds, and riverbeds.