sedimentary
Chert Nodule / Flint
Microcrystalline Quartz (SiO2)
Mohs hardness 7, brownish-tan to grey color, dull to waxy luster, conchoidal fracture, smooth microcrystalline structure, specific gravity ~2.65.
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Physical properties
Mohs hardness 7, brownish-tan to grey color, dull to waxy luster, conchoidal fracture, smooth microcrystalline structure, specific gravity ~2.65.
Formation & geological history
Formed in marine sedimentary environments through the chemical precipitation of silica-rich fluids or accumulation of siliceous organism remains (like radiolarians or sponges) within limestone or chalk beds.
Uses & applications
Historically used for knapping arrowheads and tools; currently used as aggregate, road construction material, landscaping stone, and collected as natural specimens.
Geological facts
Chert and flint were among the first geological materials utilized by early humans in the Stone Age to make sharp tools, scrapers, and fire-starting flints due to their predictable conchoidal fracture.
Field identification & locations
Identified by its extreme hardness (scratches glass), smooth waxy feel, and curved glass-like conchoidal fracture surfaces. Commonly found in limestone outcrops, riverbeds, and coastal gravels worldwide.
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