sedimentary

Chert (Flint)

SiO2 (Microcrystalline Quartz)

Hardness: 7 on Mohs scale. Color: Dark gray to brown and black with sharp edges. Luster: Waxy to vitreous. Fracture: Conchoidal. Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Dark gray to brown and black with sharp edges
Luster: Waxy to vitreous

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Dark gray to brown and black with sharp edges. Luster: Waxy to vitreous. Fracture: Conchoidal. Specific Gravity: 2.65.

Formation & geological history

Formed in marine or freshwater environments by the precipitation of silica from seawater or hydrothermal fluids, often accumulating as nodules in limestone or chalk beds.

Uses & applications

Historically used for making stone tools, arrowheads, and spark-striking flints. Modern uses include gravel aggregate, decorative stone, and lapidary work.

Geological facts

Flint was essential to early human survival as it breaks with extremely sharp edges (conchoidal fracture) perfect for knapping knives, scrapers, and arrowheads.

Field identification & locations

Identified by its glass-like sharp edges when broken, waxy surface texture, and ability to scratch glass easily. Commonly found in limestone outcrops, river beds, and coastal chalk deposits.