sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, white with brown staining, Luster: waxy to dull, Crystal structure: Microcrystalline quartz, Cleavage: none (conchoidal fracture), Specific gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, white with brown staining, Luster: waxy to dull, Crystal structure: Microcrystalline quartz, Cleavage: none (conchoidal fracture), Specific gravity: 2.6
Formation & geological history
Chemical sedimentary process involving the accumulation of silica-rich organic remains or chemical precipitation from groundwater within limestone or chalk beds.
Uses & applications
Historical toolmaking, modern abrasives, architectural accents, and road construction material.
Geological facts
Flint is a variety of chert that has been used by humans for millennia to create sharp tools and start fires due to its ability to produce sparks when struck against steel.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, fields, and sedimentary cliff faces.
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