sedimentary
Chert (Flint)
Chert (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Dark grey to brown, Luster: Waxy to vitreous, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: Dark grey to brown, Luster: Waxy to vitreous, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) on the ocean floor or from chemical precipitation. Commonly found in limestone or chalk beds.
Uses & applications
Used historically for stone tools and weapons (knapping), fire-starting (flint and steel), and currently as an additive in concrete, road base, and for gemstone tumbling/jewelry.
Geological facts
Flint was one of the most important raw materials for early humans; it breaks with sharp conchoidal edges ideal for creating knives and arrowheads.
Field identification & locations
Identify by its characteristic conchoidal (shell-like) fracture and ability to scratch glass. Found often as nodules within sedimentary rocks like limestone.
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