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 opaque brownish-gray coloration.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, and opaque brownish-gray coloration.
Formation & geological history
Formed through the replacement of limestone or chalk by silica-rich groundwater during the Paleozoic era.
Uses & applications
Historically used by indigenous peoples for making stone tools, arrowheads, and blades due to its sharp conchoidal fracture.
Geological facts
Chert nodules are extremely durable and often weather out of softer limestone matrices to form residual pebbles in glacial drift.
Field identification & locations
Easily identified in the field by its smooth, weathered cortex, conchoidal fracture scars, and high hardness that scratches glass.
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