sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: brownish-tan with iron staining, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: brownish-tan with iron staining, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the precipitation of silica from groundwater or the accumulation of siliceous organisms in marine environments. Common in limestone and dolostone formations as nodules or layers.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used in jewelry (as jasper), construction aggregate, and as a component in ceramics.
Geological facts
Because it breaks with a conchoidal (shell-like) fracture, it creates extremely sharp edges; it was once the primary material for prehistoric weaponry and tools.
Field identification & locations
Check for a smooth, waxy surface and shell-shaped fracture patterns. It will scratch glass easily. Commonly found in riverbeds or within sedimentary rock outcrops.
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