sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, or translucent brownish, Luster: waxy to dull, Crystal structure: microcrystalline (cryptocrystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or translucent brownish, Luster: waxy to dull, Crystal structure: microcrystalline (cryptocrystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the replacement of limestone. It occurs as nodules or layered deposits in various geological ages ranging from the Precambrian to recent.
Uses & applications
Used historically for stone tools and weapons (knapping), flintlock firearms, and modern decorative landscaping, jewelry (as agate/jasper variants), and industrial abrasives.
Geological facts
Chert was one of the most important materials for early humans due to its ability to split into razor-sharp edges. It is chemically identical to quartz but has a different internal structure.
Field identification & locations
Identify by its characteristic conchoidal (shell-like) fracture and sharp edges. It will scratch glass easily. Commonly found in limestone beds, chalk deposits, or as river cobbles.
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