sedimentary
Chert (flint) nodule
Microcrystalline quartz (SiO₂), commonly called chert or flint
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray, cream, and tan with a dull-to-waxy luster and no visible crystals. It has no cleavage and breaks with curved, sharp-edged conchoidal fractures; the pale outer rind may be a weathered cortex.
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Physical properties
Hardness about 7 Mohs; pale gray, cream, and tan with a dull-to-waxy luster and no visible crystals. It has no cleavage and breaks with curved, sharp-edged conchoidal fractures; the pale outer rind may be a weathered cortex.
Formation & geological history
Forms when silica precipitates or replaces carbonate-rich sediment, often around fossils or other seafloor material. Chert nodules formed in many geological periods; this image alone cannot establish the specimen’s age.
Uses & applications
Historically used for cutting tools and fire-starting; today collected, studied, and occasionally used decoratively.
Geological facts
Chert can preserve fossils and produces exceptionally sharp edges when fractured.
Field identification & locations
Look for a dense, fine-grained body, waxy appearance, and curved fracture surfaces; nodules commonly occur in limestone and chalk. The rounded shape and pale cortex are consistent with a chert nodule, though a photo cannot confirm the identification.
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