sedimentary
Chert (Nodule)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan core with grey/white outer rind, Luster: waxy to dull, Structure: microcrystalline quartz (cryptocrystalline), Cleavage: none (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: tan core with grey/white outer rind, Luster: waxy to dull, Structure: microcrystalline quartz (cryptocrystalline), Cleavage: none (conchoidal fracture)
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers, often limestone or chalk. Formed across various geological eras from the Paleozoic to the present.
Uses & applications
Historical use for stone tools and weapons due to sharp edges; currently used as aggregate, decorative stone, and sometimes in lapidary work.
Geological facts
Chert is extremely durable and chemically stable. Flints (a variety of chert) were among the first materials used by early humans to start fires and create tools.
Field identification & locations
Identify in the field by its waxy texture and shell-like (conchoidal) fractures when broken. Commonly found as nodules in limestone outcrops or as pebbles in riverbeds.
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