sedimentary
Chert (White Chert)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: White to off-white with tan rinds, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: White to off-white with tan rinds, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary basins. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a decorative stone in landscaping.
Geological facts
Chert is so hard it can scratch steel. It was one of the most important minerals for early humans because of its ability to produce sharp edges when fractured.
Field identification & locations
Identified by its waxy luster, hardness, and conchoidal (shell-like) fracture patterns. Frequently found in riverbeds or eroding out of limestone outcrops.
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