sedimentary
Chert (Flint Pepple)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Brown to tan, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown to tan, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
Formation & geological history
Formed via the accumulation of siliceous remains of microscopic organisms or through chemical precipitation in sedimentary environments; often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used as decorative gravel, in road construction, and as a semi-precious stone for tumbling.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create sharp blades and arrowheads because of its predictable conchoidal fracture.
Field identification & locations
Highly resistant to weathering; identify by its smooth, waxy feel and the way it breaks into sharp, curved edges. Frequently found in riverbeds and coastal areas.
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