sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Waxy to Dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), SG: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Waxy to Dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), SG: 2.65
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of siliceous skeletal remains of diatoms and radiolarians in marine environments. Often found in limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Today used for road surfacing, fire-starting strikers, and as a decorative landscape stone.
Geological facts
Flint is a variety of chert that produces sparks when struck against steel. It was the primary material for the Stone Age technology that allowed early humans to survive.
Field identification & locations
Identified by its extremely smooth, waxy surface and sharp, curved (conchoidal) edges when broken. Commonly found in stream beds or as nodules in limestone outcrops.
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