sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs); Color: Brownish-tan to ochre; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs)
- Color
- Brownish-tan to ochre
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs); Color: Brownish-tan to ochre; 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 or chemical precipitation in marine environments, often within limestone or shale beds. Common in various geological ages.
Uses & applications
Historically used for making stone tools and fire-starting (flint). Currently used as road aggregate, in landscaping, and as a semi-precious gemstone when polished.
Geological facts
Because it breaks with a conchoidal fracture like glass, it creates incredibly sharp edges. It was the primary material for arrowheads and scrapers for thousands of years.
Field identification & locations
Identify by its waxy appearance, extreme hardness (scratches glass), and smooth, curved fracture surfaces. Found worldwide in riverbeds and sedimentary outcrops.
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