sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish-brown, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish-brown, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from hydrothermal fluids. Commonly found in nodules within limestone or chalk beds.
Uses & applications
Historically used for stone tools/arrowheads due to its sharp edges; currently used for decorative purposes, landscaping, and as a component in road construction.
Geological facts
Chert was one of the most important materials for early humans because its conchoidal fracture allows it to be shaped into razor-sharp cutting tools. It is also often responsible for preserving fossils in high detail (silicification).
Field identification & locations
Identify in the field by its smooth, waxy texture and curved (conchoidal) breaks that look like chipped glass. It is much harder than a steel knife blade and will easily scratch glass.
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