sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, or white with conchoidal (shell-like) fracture, Luster: dull to waxy, Crystal structure: microcrystalline quartz, Cleavage: none.
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or white with conchoidal (shell-like) fracture, Luster: dull to waxy, Crystal structure: microcrystalline quartz, Cleavage: none.
Formation & geological history
Formed by the precipitation of silica in sedimentary environments, often within limestone or through the accumulation of siliceous microorganisms like diatoms or radiolarians.
Uses & applications
Historically used for stone tools and starting fires; currently used as construction aggregate, road surfacing, and in some decorative landscaping.
Geological facts
Chert was one of the most important materials for early humans because of its ability to break into extremely sharp edges. This specific specimen appears to be a weathered nodule.
Field identification & locations
Identify by its hardness (it can scratch glass and steel) and its smooth, curved fracture surfaces. Commonly found in riverbeds and limestone outcrops.
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