sedimentary

Chert (Flint / Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: Brownish-tan to caramel-yellow. Luster: Waxy to dull. Fracture: Pronounced conchoidal fracture with sharp edges. Structure: Cryptocrystalline. Cleavage: None.

Hardness: 7 on Mohs scale
Color: Brownish-tan to caramel-yellow
Luster: Waxy to dull

Identified July 23, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Brownish-tan to caramel-yellow. Luster: Waxy to dull. Fracture: Pronounced conchoidal fracture with sharp edges. Structure: Cryptocrystalline. Cleavage: None.

Formation & geological history

Formed biogenically or chemically through the precipitation of silica in marine or lacustrine sedimentary environments, often replacing carbonate rocks like limestone or chalk.

Uses & applications

Historically used for making sharp stone tools (arrowheads, scrapers) and spark-striking flints. Modern uses include lapidary, knapping, decorative stones, and aggregate.

Geological facts

Chert has been used by humans for over two million years to craft sharp tools. When struck against iron or pyrite, fine particles produce hot sparks that ignite tinder.

Field identification & locations

Identified by its high hardness (scratches glass), distinct smooth conchoidal fracture edges, and waxy luster. Widely found in gravel beds, chalk cliffs, and limestone formations globally.