sedimentary
Chert (or Flint)
Chert (SiO2)
Hardness: 7 (Mohs), Color: Tan, brown, or grey, Luster: Waxy to dull, Structure: Microcrystalline/Cryptocrystalline, Fracture: Conchoidal
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Physical properties
Hardness: 7 (Mohs), Color: Tan, brown, or grey, Luster: Waxy to dull, Structure: Microcrystalline/Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins as nodules or beds.
Uses & applications
Historically used for stone tools and fire-starting; currently used for road base, decorative landscaping, and occasionally jewelry.
Geological facts
Flint is a variety of chert that was the primary material for prehistoric arrowheads and spear points due to its sharp, predictable fracture edges.
Field identification & locations
Identify by its extreme hardness (scratches glass) and shell-like (conchoidal) fracture patterns. Found globally in limestone and chalk deposits.
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