sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Brownish-tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within other sedimentary rocks like limestone. Common in Paleozoic to Mesozoic strata.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; currently used in jewelry (as jasper), as a flux in metallurgy, and as decorative gravel.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture allows it to be 'knapped' into extremely sharp arrowheads and knives.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy luster when fresh, and distinctive shell-like (conchoidal) fracture pattern. Found globally in nodules or bedded layers.
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