sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs, Color: Black with tan/white inclusion patterns, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.8
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Physical properties
Hardness: 7 Mohs, Color: Black with tan/white inclusion patterns, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.8
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in marine environments. This specimen shows water-worn rounding.
Uses & applications
Historically used for stone tools and fire-starting; currently used for decorative gravel, landscaping, and lapidary tumbling.
Geological facts
Flint was the primary material for the Neolithic revolution, used for making arrowheads and axes. It sparks when struck against steel.
Field identification & locations
Identified by its extreme hardness (scratches glass) and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial till, and chalk deposits.
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