sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan to grayish-brown, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to grayish-brown, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed via the accumulation of siliceous remains of marine organisms or the precipitation of silica from groundwater within sedimentary rock layers like limestone.
Uses & applications
Historically used for stone tools and starting fires; modern uses include construction aggregate and decorative landscaping stones.
Geological facts
Chert has a distinct conchoidal fracture, which creates sharp edges, making it the primary material for prehistoric arrowheads and spear tips.
Field identification & locations
Identifiable in the field by its hardness (cannot be scratched by steel), waxy texture, and sharp, curved fracture patterns. Commonly found in nodules or beds within limestone formations.
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