sedimentary
Chert (River Stone)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Dirty gray/green/tan, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Fracture: Conchoidal, Specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Dirty gray/green/tan, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Fracture: Conchoidal, Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This piece shows significant rounding due to fluvial (river) erosion.
Uses & applications
Historically used for stone tools and flintknapping. In modern times, used for road aggregate or as decorative landscaping gravel.
Geological facts
Chert and flint are essentially the same material; the name 'flint' is usually reserved for dark specimens found in chalk or marly limestone. This specimen appears to have a weathered cortex.
Field identification & locations
Identifiable by its extreme hardness (will scratch glass easily) and its smooth, shell-like (conchoidal) fractures. Found in riverbeds and gravel pits worldwide.
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