sedimentary
Chert (Flint)
Microcrystalline or cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Gray and white with yellowish staining, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: Gray and white with yellowish staining, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers, often found as nodules in limestone or chalk.
Uses & applications
Historically used for making stone tools (arrowheads, knives) and starting fires. Modern use includes landscaping, road construction, and as a collector's specimen.
Geological facts
Flint was one of the most important minerals for early human survival, providing both sharp tools and a means to create sparks for fire. When broken, it creates incredibly sharp edges only a few molecules thick.
Field identification & locations
Identify in the field by its very smooth, shell-like (conchoidal) fracture and its ability to scratch glass or steel. Often found in riverbeds or eroded out of limestone cliffs.
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