sedimentary
Chert (Flint)
Chert (SiO2)
Hardness: 7 (Mohs scale), Color: White to light grey with translucent center, Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light grey with translucent center, Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed by the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins. This specimen shows a distinct white weathering rind (patina) around a microcrystalline core.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp conchoidal fracture. Modern uses include road surfacing, decorative gravel, and as high-silica industrial feedstock.
Geological facts
Flint is a variety of chert predominantly found in chalk and marly limestone. It was the building block of the Stone Age, allows humans to create fire through sparks when struck against steel.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy luster on fresh breaks, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds or limestone outcrops.
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