sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, or brown, Luster: waxy to dull, Structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or brown, Luster: waxy to dull, Structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; commonly found in limestone or chalk beds.
Uses & applications
Used historically for stone tools and weapons (arrowheads), as a fire-starter, and currently in construction aggregate or as a lapidary material.
Geological facts
Chert is so hard it can scratch steel. The sharp edges created by its conchoidal fracture made it the premier material for prehistoric toolmaking globally.
Field identification & locations
Look for a smooth, waxy surface and shell-like (conchoidal) fractures. Often found as nodules or layers within sedimentary rock formations.
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