sedimentary
Chert (Jasper / Flint Variant)
Microcrystalline Quartz (SiO2)
Mohs hardness 7. Waxy to dull luster, conchoidal fracture, opaque to translucent edges. Color palette includes tan, brown, black, and orange iron oxide staining.
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Physical properties
Mohs hardness 7. Waxy to dull luster, conchoidal fracture, opaque to translucent edges. Color palette includes tan, brown, black, and orange iron oxide staining.
Formation & geological history
Formed via precipitation of silica-rich fluids or accumulation of micro-fossil siliceous tests (radiolaria/diatoms) in sedimentary basins, followed by diagenesis.
Uses & applications
Historically used for knapping stone tools, arrowheads, and fire-starting flint. Currently used as gravel, landscape stone, and for lapidary tumbling.
Geological facts
Chert has been used by early humans for hundreds of thousands of years due to its sharp conchoidal fracturing edges when struck.
Field identification & locations
Identified by high hardness (scratches glass, cannot be scratched by steel), smooth conchoidal fracture faces, and waxy luster. Commonly found in riverbeds and limestone formations.
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