sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale. Color: Light grey to brownish-grey. Luster: Waxy to dull. Fracture: Distinctive conchoidal fracture producing sharp edges. Structure: Cryptocrystalline micro-quartz.

Hardness: 7 on Mohs scale
Color: Light grey to brownish-grey
Luster: Waxy to dull

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Light grey to brownish-grey. Luster: Waxy to dull. Fracture: Distinctive conchoidal fracture producing sharp edges. Structure: Cryptocrystalline micro-quartz.

Formation & geological history

Formed in marine or freshwater sedimentary environments via the precipitation of silica from seawater or biochemical accumulation of siliceous organisms like radiolaria and sponges.

Uses & applications

Historically used for making stone tools, arrowheads, and spark-producing fire strikers. Modern uses include decorative gravel and lapidary practice.

Geological facts

Chert and flint were among the earliest materials manipulated by prehistoric humans to craft sharp cutting tools and arrowheads due to its predictable conchoidal fracturing.

Field identification & locations

Identified by its fine-grained texture, waxy luster, hardness (scratches glass), and sharp conchoidal edges. Widely found in limestone and chalk formations worldwide.