sedimentary
Chert (Jasper / Flint)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness 7 on Mohs scale, earthy tan to brown-yellow mottling, dull to vitreous/waxy luster, microcrystalline/cryptocrystalline texture, shell-like (conchoidal) fracture, specific gravity around 2.65
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Physical properties
Hardness 7 on Mohs scale, earthy tan to brown-yellow mottling, dull to vitreous/waxy luster, microcrystalline/cryptocrystalline texture, shell-like (conchoidal) fracture, specific gravity around 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from chemical fluids in sedimentary marine or lake environments, often replacing original limestone or dolomite beds.
Uses & applications
Historically used for stone tools, arrowheads, and spark-striking flints due to its hardness and sharp conchoidal fracturing. Modern usage includes road aggregate, landscaping stone, and lapidary tumbling.
Geological facts
Chert is so fine-grained that its individual quartz crystals cannot be seen without an electron microscope. Native Americans favored high-quality chert and jasper for crafting projectile points.
Field identification & locations
Look for a smooth, glass-like fracture surface with sharp edges when broken, along with a high hardness that easily scratches steel and glass. Extremely common in limestone terrains, gravel beds, and river basins worldwide.
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