sedimentary
Chert (Flint/Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs), Color: Tan, brown, and yellowish-orange, Luster: Waxy to dull, Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs), Color: Tan, brown, and yellowish-orange, Luster: Waxy to dull, Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone or as nodules in soil.
Uses & applications
Historically used for making stone tools (arrowheads); currently used in jewelry (as jasper), construction aggregate, and as a starting material for fire (flint).
Geological facts
Chert has been used by humans for hundreds of thousands of years to create sharp-edged tools because of its unique conchoidal fracture pattern.
Field identification & locations
Identified by its extreme hardness (scratches glass), waxy texture when broken, and sharp edges. Extremely common in riverbeds and limestone outcrops.
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