sedimentary
Chert (Tripolitic Chert / Flint Nodules)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: tan, cream, and brown mottled, Luster: dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, cream, and brown mottled, Luster: dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, specific gravity: 2.65
Formation & geological history
Formed through the replacement of limestone or chalk by silica-rich fluids. Often found as nodules within carbonate sedimentary layers, reflecting ancient marine environments.
Uses & applications
Historically used for stone tools and arrowheads. Modern use includes landscaping, decorative stones, and as a source of silica for industrial glass production.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges for cutting. When struck against steel, it can produce sparks, leading to its name 'flint' in specific color varieties.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel nail) and the way it breaks into smooth, curved plates (conchoidal fracture). Commonly found in limestone outcrops or riverbeds near sedimentary basins.
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