sedimentary
Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Dull to Waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Dull to Waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone environments and as stream-rounded pebbles.
Uses & applications
Historically used for stone tools and starting fires (flint). Currently used in road construction, landscaping, and as an abrasive.
Geological facts
Chert is extremely durable and chemically stable, often surviving heavy erosion. It was the primary material for arrowheads and scrapers in many prehistoric cultures.
Field identification & locations
Identify by its extreme hardness (scratches glass), smooth waxy feel when freshly broken, and conchoidal fracture patterns. Found globally in riverbeds and coastal deposits.
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