sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Dark grey to black with reddish inclusions, Luster: Vitreous to waxy, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified July 15, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Dark grey to black with reddish inclusions, Luster: Vitreous to waxy, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Chemical sedimentary rock formed from the accumulation of microscopic silica-rich organisms (like radiolarians) or inorganic precipitation within limestone/chalk beds during various geological eras (Paleozoic to Mesozoic).

Uses & applications

Historically used for making stone tools (arrowheads, knives), striking fire, and flintlock firearms. Today used as road aggregate or as an ornamental stone in jewelry (when colorful).

Geological facts

Flint is a variety of chert that occurs in chalk or marly limestone. It was the primary material for the Neolithic 'stone age' technology due to its ability to hold a sharp edge.

Field identification & locations

Identify by its characteristic conchoidal fracture (curved, glass-like breaks) and ability to scratch glass. Commonly found in nodules within limestone formations or as weathered pebbles in riverbeds.