sedimentary
Chert (Flint / Chalcedony)
Silicon Dioxide (SiO2)
Hardness 6.5-7 on the Mohs scale, waxy to vitreous luster, sharp conchoidal fracture, microcrystalline texture, yellowish-tan to translucent brown coloration.
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Physical properties
Hardness 6.5-7 on the Mohs scale, waxy to vitreous luster, sharp conchoidal fracture, microcrystalline texture, yellowish-tan to translucent brown coloration.
Formation & geological history
Formed as a chemical sedimentary rock through the precipitation of silica-rich fluids or accumulation of siliceous organism remains (like radiolarians or diatoms) in marine sediments.
Uses & applications
Historically used for stone tools, arrowheads, and fire-starting flints. Currently used in knapping, landscaping, and aggregate.
Geological facts
Chert fractures with extremely sharp edges, making it one of the earliest raw materials human ancestors used for toolmaking.
Field identification & locations
Identified by its hardness, smooth waxy surface, and characteristic curved, shell-like (conchoidal) fractures. Found in limestone nodule beds and gravel deposits worldwide.
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