sedimentary
Chert/Flint
Silicon dioxide (SiO2)
Hardness: 7 (Mohs), Color: Dark gray, black, brown, Luster: Waxy to dull, Crystal structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.59-2.65
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Physical properties
Hardness: 7 (Mohs), Color: Dark gray, black, brown, Luster: Waxy to dull, Crystal structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.59-2.65
Formation & geological history
Forms as nodules in sedimentary rocks, often limestone or chalk, from the accumulation of silica-rich marine organisms like diatoms and radiolarians.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) and striking fire. Occasionally polished for jewelry.
Geological facts
Flint was crucial to early human survival for tool making and fire starting due to its hardness and ability to fracture with sharp edges.
Field identification & locations
Identify by its waxy luster, smooth surface, conchoidal fracture (curved breakages), and high hardness (scratches glass). Found globally in sedimentary deposits.
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