sedimentary
Chert (varietal: Flint/Jasper)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs), Color: Tan to light brown, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs), Color: Tan to light brown, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the precipitation of silica in groundwater or through the accumulation of silica-rich organic remains (like diatoms) in marine environments. Often found as nodules in limestone or chalk.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used as high-quality aggregate in construction, gemstones (jasper), and striking tools to create sparks.
Geological facts
Chert breaks with a conchoidal fracture, producing very sharp edges, which made it a critical material for prehistoric tool manufacturing and weaponry.
Field identification & locations
Identify by its hardness (scratches glass), waxy luster on fresh surfaces, and smooth concave breakage patterns. Found globally in sedimentary basins.
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