sedimentary
Chert (Chalky Flint Node)
Chert (Microcrystalline Quartz, SiO2)
Hardness: 7 Mohs; Color: White/cream weathered exterior, often brown or grey interior; Luster: Dull to waxy; Crystal structure: Trigonal/Cryptocrystalline; Conchoidal fracture.
- Hardness
- 7 Mohs
- Color
- White/cream weathered exterior, often brown or grey interior
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 Mohs; Color: White/cream weathered exterior, often brown or grey interior; Luster: Dull to waxy; Crystal structure: Trigonal/Cryptocrystalline; Conchoidal fracture.
Formation & geological history
Formed through the chemical precipitation of silica in sedimentary environments, often replacing carbonate material in chalk or limestone beds. Common in Cretaceous and Jurrasic deposits.
Uses & applications
Historically used for stone tools and weapons (flint-knapping); currently used in road construction, as decorative gravel, and occasionally for fire-starting.
Geological facts
Flint was the primary resource for humanity's early technology, used to create the sharpest blades and first man-made fires by striking against iron pyrite.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) breakage pattern. Found globally in limestone/chalk outcrops or river beds.
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