sedimentary
Chert
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, colors range from white and gray to brown, black, or reddish-brown due to impurities.
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Physical properties
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, colors range from white and gray to brown, black, or reddish-brown due to impurities.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions, often replacing limestone or accumulating from the skeletal remains of silica-secreting organisms like radiolarians and diatoms, spanning various geological ages.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-fire implements due to its sharp conchoidal fracture. Also used in aggregate and landscaping.
Geological facts
Chert is extremely durable and weather-resistant, which is why ancient stone tools made from it survive exceptionally well in the archaeological record.
Field identification & locations
Can be identified by its hardness (scratches glass), waxy luster, and distinctive conchoidal fracture. Commonly found embedded in limestone or chalk formations worldwide.
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