sedimentary
Chert (Flint)
Chert (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, white with brown inclusions, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, white with brown inclusions, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary basins. This often occurs as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools (knapping) and fire-starting. Currently used in road surfacing, decorative landscaping, and occasionally as a gemstone in jewelry.
Geological facts
Flint is a variety of chert. It was the primary material for the Stone Age technology due to its ability to produce razor-sharp edges when broken.
Field identification & locations
Identify in the field by its conchoidal (shell-like) fracture, ability to scratch glass, and waxy texture on fresh surfaces. Often found in riverbeds or within limestone outcrops.
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