sedimentary
Chert nodule
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, and typically brown, gray, or black coloration.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, and typically brown, gray, or black coloration.
Formation & geological history
Formed through the replacement of limestone or chalk by silica-rich solutions during deep burial and diagenesis over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-striking fire starters due to its sharp conchoidal fracture.
Geological facts
Chert nodules commonly weather out of chalk and limestone cliffs as distinct, potato-like lumps with a rough white cortex.
Field identification & locations
Identify in the field by its extreme hardness, smooth conchoidal breakage, and frequent occurrence as nodules within sedimentary limestone formations.
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