sedimentary
Chert (Flint nodule)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness 6.5-7 Mohs, waxy to dull luster, conchoidal fracture, cryptocrystalline structure, brown to dark gray body with a weathered whitish patina/cortex.
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Physical properties
Hardness 6.5-7 Mohs, waxy to dull luster, conchoidal fracture, cryptocrystalline structure, brown to dark gray body with a weathered whitish patina/cortex.
Formation & geological history
Formed biochemically or chemically through the diagenetic replacement of carbonate rocks by precipitated silica in marine sediments.
Uses & applications
Historically used for stone tools, flintknapping, and spark ignition; currently used for lapidary accents, road metal, and aggregate.
Geological facts
Chert nodules often nucleate around ancient burrow tracks or marine organic remains like sponges and radiolarians.
Field identification & locations
Identified in the field by its high hardness (scratches glass), smooth conchoidal fractures, and sharp edges; commonly found in limestone or chalk beds.
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