sedimentary
Chert Nodule
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectMohs hardness of 7; conchoidal fracture; waxy to vitreous luster; translucent to opaque brownish-red color.
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Physical properties
Mohs hardness of 7; conchoidal fracture; waxy to vitreous luster; translucent to opaque brownish-red color.
Formation & geological history
Formed through the chemical precipitation of silica in marine limestone or chalk environments during the Cenozoic or older eras.
Uses & applications
Used historically for primitive stone tools and fire-starting; currently collected as a geological specimen.
Geological facts
Texas regional geology around San Antonio frequently yields chert and flint nodules weathered out from Cretaceous limestone formations.
Field identification & locations
Identify by its extreme hardness, sharp conchoidal edges, and smooth weathered exterior cortex. Common in gravel beds and limestone creeks.
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